&ii:mimrkm^mmMMmmmmmmma:/-r!fmi^,;mm:, 


Colombia  MnttJem'tp 
mttjpiCitpoflriotork 

College  of  ^i)^&itianfi  atiis  gjurgeonsS 
ILifararp 


Gipf    Of^ 

Dr.  M  A  .  st^RR 


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Architecture  of  the  Brain 


WH.  FULLER,  M.  D. 

Formerly  Demonstrator   of  Anatomy,   McGill  College;   Professor  of 

Anatomy,  Bishop's  College,  Montreal,  Canada;   Member 

of  the  American  Medical  Association,   etc. 


ILLUSTRATED. 


GRAND  RAPIDS,  MICH. 

J  896. 


\  M  455- 


Cofyright,    rSgb. 

WM.  FULLER,  M.  D. 

AIL  rights  reserved. 


Press  of 

Seymour  Ss'  Midr  Prhiting  Co., 

Grand  Rapids,  Mich. 

Engravings  by 
Grand  Rapds  Engraving  Co. 


NTRODUCTION. 


In  the  following  desci'iption  of  the  Central  Nervous 
System  it  is  not  intended  to  rehearse  minute  details  which 
can  be  found  in  the  many  excellent  works  upon  anatomy, 
but  to  place  in  view  in  as  clear  and  concise  a  manner  as  pos- 
sible the  general  architecture  of  the  central  nervous  system, 
and  to  trace  the  relation  and  continuity  of  its  pai'ts.  When 
a  general  knowledge  of  the  structure  of  the  brain  is  acquired 
by  the  student  a  useful  and  practical  step  is  gained,  because 
he  will  not  oiily  be  able  to  describe  the  situation  of  a  lesion 
and  understand  the  descriptions  made  by  others,  but  he  will 
be  in  a  situation  to  intelligently  discuss  the  functions  of  its 
parts,  and  is  prepared  to  work  in  the  field  of  discov- 
ery. The  incidental  assignment  of  function  to  any  j)art  of 
the  nervous  system  in  these  pages  is  intended  to  assist  the 
memory  and  awaken  enquiry.  Nothing  stimulates  the  obser- 
vation to  the  same  extent  as  the  entertainment  of  a  theory, 
to  be  demonstrated  or  corrected  by  careful  observation  of 
facts  which  fall  under  one's  own  notice,  or  by  those  which  can 
be  obtained  from  other  reliable  sources. 

The  following  description  has  been  made  from  dissections 
by  the  author,  and  has  been  carefully  verified  by  a  comparison 
of  longitudinal  and  lateral  dissections,  and  by  sections,  all  of 
which  agree  in  proving  the  correctness  of  the  representations 
herein  described. 

These  dissections  have  been  permanently  recorded  by 
castings  in  plaster,  and  the  sections  have  been  photographed 


4  ARCHITECTURE    OF   THE    BRAIN. 

and  plates  made,  so  that  both  the  casts  and  the  plates  can  be 
repeated  at  pleasure,  thus  enabling  any  who  may  take  an 
interest  in  the  anatomy  of  the  brain  to  acquire  a  knowledge 
of  it  with  ease. 

A  cast  is  much  superior  to  a  picture,  since  it  represents 
correctly  the  size,  relation  and  direction  of  the  parts  in  a 
much  plainer  manner  than  can  be  done  by  a  plate. 

The  plates  introduced  for  illustration  are  drawn  from  the 
casts  of  dissections  and  refer  to  them. 

In  order  to  bring  the  means  of  acquiring  a  knowledge  of 
this  important  department  of  medical  science  within  the  reach 
of  all,  an  Anatomical  Company  has  been  formed  to  reproduce 
the  casts  and  plates  at  a  very  moderate  pi'ice. 


THE  MEMBRANES  OF  THE  BRAIN. 


The  Central  Nervous  System,  or  the  Cerebro-Spinal  axis, 
is  contained  in  the  cavity  of  the  cranium  and  spinal  canal. 
This  cavity  is  lined  by  a  tough  fibrous  membrane,  the  dura 
mater,  which  is  closely  adherent  to  the  inner  surfaces  of  the 
bones  of  the  skull,  especially  at  the  sutures,  base,  and 
the  mai'gin  of  the  foramen  magnum,  but  is  loosely  at- 
tached by  fibrous  tissue  to  the  bones  forming  the  spinal 
canal.  Its  internal  surface  is  smooth,  covered  by  a  serous 
surface  which  is  the  outer  wall  of  the  arachnoid  cavity,  and 
it  is  perforated  by  numerous  openings  corresponding  to  the 
foramina  of  its  bony  enclosure.  These  openings  are  for  the 
transmission  of  nerves  and  blood  vessels,  and  the  membrane 
is  prolonged  outwards,  to  be  continuous  with  their  sheaths  and 
with  the  periosteum  of  the  skull.  As  an  instance,  the  dura 
mater  forms  a  sheath  for  the  optic  nerve,  expands  to  form 
sclerotic  coat  of  the  eyeball  and  lines  the  walls  of  the  orbit. 
The  dura  mater  contains  between  its  layers  the  meningeal 
arteries  and  channels  for  the  conveyance  of  venous  blood, 
called  sinuses.  The  falx  cerebri  and  the  tentorum  cerebelli 
are  projections  of  the  dura  mater  extending  into  the  fissures 
of  the  brain,  respectively  between  tlie  hemispheres  of  the 
cerebrum  and  between  the  occipital  lobes  and  the  cerebellum. 
The  use  of  these  processes  are  to  sustain  the  parts  of  the 
brain  in  their  proper  pjosition. 

The  arachnoid  is  a  thin  fibrous  m^^mbiane  which  surrounds 
the  brain,  spmal  cord  and  the  roots  of  the  nerves.      It  covers 


b  AECHITECTURE    OF   THE   BRAIN. 

the  convolutions  of  the  brain,  but  does  not  dip  into  the  sulci 
between  them.  It  is  somewhat  loosely  attached  to  the  sur- 
face of  the  brain,  but  closely  adherent  to  the  pons,  medulla 
and  spinal  cord,  as  well  as  to  the  roots  of  the  nerves  which 
it  encloses  and  supports  between  their  origin  and  the  fora- 
mina of  the  dura  mater  before  mentioned.  The  intervals 
between  the  arachnoid  membrane  and  the  pia  mater  beneath 
are  called  the  sub-arachnoid  spaces.  These  communicate 
with  each  other  and  with  the  ventricles  of  the  brain  and  in 
certain  pathological  conditions  are  the  seat  of  effusion.  The 
arachnoid  is  continuous  with  the  inner  serous  surface  of  the 
dura  mater  enclosing  the  arachnoid  cavity.  Upon  each  side 
of  the  spinal  cord,  between  the  roots  of  the  nerves  and 
throughout  its  whole  length,  this  membrane  sends  out  deli- 
cate projections  which  are  attached  to  the  inner  surface  of  the 
dura  mater,  the  function  of  which  is  to  preserve  the  position 
of  the  spinal  cord  in  the  spinal  canal.  Together  they  are 
called  the  ligamentum  dentatum. 

The  pia  mater  immediately  invests  the  nervous  sub- 
stance of  the  brain  and  spinal  cord,  is  the  vascular  membrane, 
and  is  made  up  of  an  intricate  network  of  blood  vessels  of 
various  sizes, which  break  up  into  numerous  minute  vessels  that 
penetrate  the  nervous  mass  and  are  distributed  to  it.  In  a  sec- 
tion of  the  brain  these  vessels  are  divided  and  are  seen  as 
points  or  specks  on  the  surface  of  the  section,  and  are  called 
puncta  vasculosa.  Those  blood  vessels  which  are  distributed 
to  the  grey  masses,  or  nerve  centres  within  the  brain,  are  large 
and  numerous,  while  those  in  the  white  matter  are  smaller 
and  fewer  in  number.  Projections  of  the  pia  mater  extend 
through  fissures  into  the  ventricles,  or  cavities  within  the 
brain,  with  which  they  will  be  described.  Attached  to  these 
projections  of  the  pia  in  the  ventricles  are  several  close  capillary 


THE    MEMBRANES.  7 

networks,  one  for  each  ventricle,  which  are  called  the  choroid 
plexuses  and  which  will  also  be  described  with  the  ventricles  of 
the  brain.  The  network  of  blood  vessels  constituting  the  pia 
mater  is  held  together  and  supported  by  fine  filaments  of 
fibrous  tissue  attached  on  the  outer  side  to  the  inner  surface  of 
the  arachnoid  membrane,  and  on  the  inner  extending  into  the 
substance  of  the  brain  with  the  framework  of  which  it  is  con- 
tinuous. The  arachnoid  membrane  before  described  is  a 
condensation  of  the  fibrous  tissue  of  the  pia  mater  over  the 
surface  of  the  brain  covered  externally  by  a  serous  sur- 
face, in  the  same  manner  as  the  internal  surface  of  the  dura 
mater  is  covered  internally  by  a  membrane  of  the  same 
serous  character.  These  serous  surfaces  are  continuous, 
therefore  it  may  be  said,  that  in  reality  there  are  but  two 
membranes  of  the  brain,  viz. ,  the  dura  mater  and  the  pia 
mater,  each  having  a  serous  surface  which  together  enclose  a 
serous  cavity. 

To  sum  uj) :  The  brain  is  supplied  with  a  dura  mater  for 
protection,  the  arachnoid  to  accommodate  its  movements  and 
the  pia  mater  to  provide  for  its  nourishment. 


THE  CEREBRO  SPINAL  AXIS. 


The  mass  of  nervous  matter  included  under  this  heading 
is  commonly  referred  to  as  the  brain  and  spinal  cord.  The 
brain  is  that  portion  of  it  which  is  contained  within  the 
cranial  cavity,  and  the  spinal  cord  is  the  part  suspended 
within  the  spinal  canal.  In  this  description  we  will  view  the 
axis  as  an  isolated  object,  and  the  divisions  of  it  made  for 
the  convenience  of  description,  will  be  marked  by  distinctions 
upon  the  axis  itself,  without  any  reference  to  the  relations  of 
its  parts  to  those  of  any  other  part  of  the  body. 

After  giving  a  genei'al  description  of  the  structure  of  any 
part,  we  will  direct  the  attention  to  the  natural  order  of  dis- 
section from  above  downwards,  as  represented  by  the  castings 
before  referred  to,  which  are  intended  to  accompany  and 
illustrate  these  pages. 

When  the  anatomy  of  the  spinal  cord  has  been  reached  in 
the  order  of  description  and  studied,  its  various  columns  will 
be  traced  upwards  to  their  associations  above,  by  which  a 
complete  review  of  the  whole  will  be  brought  before  the 
mind  and  its  parts  associated  into  the  formation  of  a  structure. 

A  very  proper  and  convenient  di  vision  of  the  cerebro  spinal 
axis  is  the  ce7^ebrum,  cerebellum  and  spinal  cord  with  their 
respective  conections,  and  in  this  description  we  will  follow 
the  divisions  commonly  in  use  though  without  strict  adherence 
to  old  boundaries.  We  will,  for  instance,  say  that  the  cere- 
brum is  all  that  portion  of  the  brain  above  the  pons  Varolii, 
including  the  hemispheres  their  peduncles  and  commissures. 


THE    CEREBRO    SPINAL    AXIS.  V 

The  cerebellum  and  pous  will  be  described  together,  on  ac- 
count of  the  close  association  of  their  parts  and  the  necessity 
of  maintaining  the  analogy  between  this  structure  and  that 
of  the  cerebrum.  Tlie  medulla  oblongata  will  be  outlined, 
as  that  portion  of  the  spinal  cord  which  extends  from  the 
lower  border  of  the  pons  Varolii  to  the  lower  part  of  the 
decussation  of  the  anterior  pyramids  of  the  medulla,  below 
which  point  is  the  spinal  cord  proper. 

Viewed  as  a  whole  the  cerebro  spinal  axis  presents  two 
lateral  halves,  united  by  commissures  and  divided  in  the  mid- 
dle before  and  behind  by  a  continuous  but  modified  longi- 
tudinal fissure,  which  in  front  is  called  the  anterior  and 
behind  the  posterior  median  fissure. 

The  Median  Fissure. — The  median  fissure  divides  the 
axis  into  lateral  halves  and  has  diflferent  names  applied  to  it 
in  the  difi'erent  localities  in  which  it  lies.  In  front  of  the 
spinal  cord  it  is  called  the  anterior  median  fissure,  which  is 
partially  interrupted  at  about  an  inch  below  the  pons  Varolii 
by  the  decussation  of  the  anterior  pyramids  of  the  medulla  ob- 
longata. Unless  the  groove  upon  the  front  of  the  pons  Varolii 
which  lodges  the  basilar  artery  may  be  called  a  continuation  of 
the  anterior  median  fissure,  this  fissure  is'  completely  inter- 
rupted to  the  extent  of  about  one  and  half  an  inch  by  the 
transverse  fibres  of  the  pons.  Above  the  pons,  this  fissure 
is  broad  and  expanded  between  the  peduncles  of  the  cere- 
brum, where  it  is  called  the  interpeduncular  space,  in  front  of 
which,  at  its  termination  in  the  great  longitudinal  fissure  of  '"■ss. 
the  cerebrum,  it  is  interrupted  by  the  optic  commissure. 

The  sides  of  the  interpeduncular  space  are  connected  in 
front  with  the  commencement  of  the  fissures  of  Sylvius,  and 

Note.— The  vertical  sections  are  numbered  separately  to  indicate  the  situation  of  each  cut 
upon  plates  25  and  26  and  are  marked  by  a  *  thus  (26*).  The  general  plates  are  referred  to  by  simple 
numbers. 


edian  fissure 


Compan 


10  AECHITECTUKE    OF    THE    BRAIN. 

behind  with  the  lateral  extremities   of   the  great  transverse 
fissure. 
Great  longitudinal  The  great  longitudlnal  fissure  separates  the  hemispheres 

2-17-24-26.  of  the  cerebrum  from  each  other,  it  averages  about  two  and 

one-half  inches  in  depth,  and  at  its  bottom  is  the  corpus  cal- 
losum,  the  great  commissure  of  the  cerebrum  which  unites  the 
hemispheres.  Behind  the  posterior  extremity  of  the  corpus  cal- 
losum  this  fissure  joins  the  great  transverse  fissure,  which  it 

Intersection   with.  ,  'inpii  ti  it  * 

transverse  fissure  lotersects  lu  the  middle  or  the  latter.  Beneath  the  posterior 
extremity  of  the  corpus  callosum  both  communicate  with  the 
cavity  of  the  third  ventricle.     A  process  of  pia  mater,  called 

^'tmn'^Ff'"''"^''  ^^^  velum  interpositum,  passes  through  this  opening  or  fissure, 
the  fissure  of  Bichat,  into  the  third  ventricle.     A  longitudinal 

Groove.  Fig.  8.  groove  Separating  the  tubcrcles  of  the  corpora  quadrigemina, 
and  lower  down  a  depression  upon  the  upper  surface  of  the 
valve  of  Vieussens,  mark  the  continuation  of  the  median  fis- 
sure, which  is  now  interrupted  by  the  cerebellum.  The  fissure  is 

incisura.  Figs.  27-  indicated  upon  the  cerebellum  by  a  notch  in  front  and  one 
behind,  the  incisuia  anterior  and  posterior  of  the  cerebellum. 

Posterior  median      Bclow  the  cerebellum,  the  posterior  median  fissure  begins  at 

fissure.     Figs.  8-  '  r  ^  S 

■0  the    lower   extremity  of   the   fourth  ventricle,   and  extends 

throughout  the  length  of  the  spinal  cord.  The  posterior 
median  fissure  of  the  spinal  cord  is  deeper  and  narrower  than 
the  anterior,  and  its  sides  are  more  difficult  to  separate. 

The  ventricular  system. — In  the  centre  of  the  mass 
throughout  its  whole  length  is  a  cavity  or  ventricle  which  is  also 
modified  at  different  points  along  its  course.  In  the  spinal  cord 
it  is  a  slender  canal  which,  behind  the  medulla  oblongata,  con- 
nects with  the  posterior  median  fissure  by  an  interruption  of  the 
posterior  commissure  of  the  spinal  cord.  At  this  point,  on 
account  of  the  lateral  separation  of  the  posterior  columns  of 
the  cord,  the  minute  canal  expands  into  a  broad  cavity,  the 


:entral  canal  of 
spinal  cord.  Figs. 
8-10. 


TUB    CEREBRO    SPINAL    AXIS> 


11 


fourth  ventricle,  which  is  situated  behind  the  upper  half  of 
the  medulla  oblongata  and  the  pons  Varolii,  and  is  beneath  the 
cerebellum.  Above  the  pons,  the  cavity  of  the  fourth  ventricle 
is  contracted  into  a  canal  about  the  size  of  a  small  quill, 
the  iter,  which  is  about  five-eighths  of  an  inch  in  length,  lies 
beneath  the  optic  lobes  and  between  the  crura  of  the  cerebrum, 
and  connects  the  third  and  fourth  ventricles  of  the  brain. 

The  iter  terminates  above  in  a  vertical  slit,  the  third 
ventricle,  situated  between  the  opposed  sides  of  the  thalami 
optici,  or  basal  ganglia  of  the  cerebrum.  The  third  ventricle 
reaches  below  to  the  base  of  the  brain,  and  above  extends  lat- 
erally outward  over  the  thalami  to  the  edges  of  the  fornix, 
beneath  the  margins  of  which  it  is  continuous  with  the  lateral 
ventricles  of  the  hemispheres.  The  lateral  ventricles  are 
large  cavities,  one  in  tha  center  of  each  hemisphere,  pro- 
longations of  which  extend  into  the  lobes  of  the  hemispheres, 
and  are  called  the  anterior,  middle  and  posterior  corima  of 
the  lateral  ventricles. 

Thus  it  may  be  said  that  the  cerebro  spinal  axis  is  a  hoi 
low  tube  of  nervous  matter  divided  into  lateral  halves  which 
are  separated  by  a  fissure  and  united  by  a  commissure.  The 
cavities  Avill  be  again  described  in  connection  with  the  parts 
that  enclose  them. 


Fourth  ventrici 
compose  fifiuri 
8-10-13  15  26. 


THE  CEREBRUM. 


Superior  surface. 
Figs.  1-24  26. 


Inferiors 
Figs.  2-' 


Frontal  surface 


Olfactory  i 
bulbs  and  fissure. 
Figs.  2-7. 

Temporal  lobes. 


THE    SURFACE. 

Separated  from  the  rest  of  the  mass  of  the  Central  Ner- 
vous System  and  viewed,  the  cerebrum  is  much  the  largest 
part,  being  about  eight  times  the  weight  of  the  cerebellum, 
and  thirty  times  that  of  the  spinal  cord.  It  averages  seven 
inches  in  a  longitudinal  and  five  inches  in  a  transverse  diame- 
ter. It  is  convex  upon  its  upper  surface,  and  its  sides 
seen  from  above,  present  an  oval  contour. 

Turned  over,  its  under  surface  in  a  general  aspect  is  oval 
and  flat.  This  surface  presents  three  lobes  and  two  surfaces, 
and  is  divided  into  lateral  halves  by  a  continuation  of  fissures 
and  depressions. 

The  anterior  or  frontal  portion  is  a  flattened  surface  divided 
in  the  middle  by  the  anterior  median  fissure.  The  marginal 
convolutions,  which  form  the  sides  of  the  fissure,  are  elevated 
above  the  rest  of  the  surface,  and  the  parts  upon  each  side 
of  the  elevation  are  triangular  and  slightly  concave,  corres- 
ponding to  the  upper  surfaces  of  the  orbital  plates  of  the 
frontal  bone,  upon  which  they  rest  in  their  normal,  position 
in  the  cranial  cavity.  On  the  sides  of  the  median  fissure,  and 
removed  half  an  inch  from  it,  are  two  other  fissures,  one  on 
either  side,  which  run  parallel  to  it  and  lodge  the  olfactory 
bulbs  and  nerves. 

The  temporal  lobes  project  above  this  surface  behind  like 
large  tubercles,  one  on  each  side,  and  are  separated  from 
each  other  by  a  considerable  interval.    They  are  divided  from 


THE    CEREBRUM. 


13 


the  frontal  surface,  or  lobes,  by  the  fissures  of  Sylvius  which 
arch  around  and  constrict  their  bases. 

The  posterior,  or  occipital  lobes,  are  directed  backwards, 
are  pointed  posteriorly,  and  are  separated  from  each  other  by 
the  posterior  median  fissure,  which  in  this  situation,  longitudin- 
ally, is  about  three  inches  in  depth,  running  forward  as  far  as 
the  posterior  border  of  the  corpus  callosum. 

The  contour  presented  by  a  view  of  the  under  surfaces  of  the 
temporal  and  occipital  lobes  is  oval,  concave  from  before 
backwards  and  from  side  to  side,  forming  a  shallow  cup,  in 
the  center  of  which  is  an  oval  opening.  This  opening 
is  the  hilus  of  the  cerebrum  w^hich  transmits  the  cerebral 
peduncles  in  front,  and  behind  lodges  the  optic  lobes,  or 
corpora  quadrigemina.  In  front  of  this  opening,  between  the 
temj^oral  lobes,  is  an  interspace,  the  iioor  of  which  contains 
the  optic  commissure,  iufundibulum,  corpora  albicantia  and 
posterior  perforated  space.  These  parts  rest  upon  the  body 
of  the  sphenoid  bone.  The  posterior  median  fissure  extend- 
ing backward  completes  the  division  of  the  surface  into  lateral 
halves. 

The  anterior  portions  of  this  surface,  or  the  temporal 
lobes,  are  lodged  in  the  temporal  fossae  of  the  skull,  and  the 
occipital  lobes  rest  upon  the  tentorium  cerebelli.  This  sur- 
face behind  forms  the  upper  boundary  of  the  extra  ventricular 
portion  of  the  great  transverse  fissure  or  fissure  of  Bichat. 

The  cerebrum  is  divided  into  lateral  halves,  called  hemis- 
pheres, by  the  great  longitudinal  fissure,  which  includes  the 
anterior  and  posterior  median  fissures  that  separate  the  frontal 
and  the  occipital  lobes.  The  hemispheres  are  united  at  the  base 
of  the  cerebrum,  and  by  several  commissures  the  largest  of 
which  is  the  corpus  collosum  or  the  great  transverse  commis- 
sure of  the  cerebrum. 


'issiirc  of  Sylviu 
Figs.  3-7-16-24. 


Occipital  lobe 
posterior  nn 
fissure. 


Hilus  of  cerebrum 
and  of  the  hem- 
ispherical gansli- 


and  i 


-issure  of  Bichat 
in  Fig.  2  bounds 
the  hilus  on  its 
sides  and  behind. 
The  ventricular 
extremity.  Figs.  -1 
Its  infer- 


Fig.   17. 
n  called 


Corpus  callosum. 
Figs.  3  S  23-26 


Compare  convolu 
tioiis  and  iissures 
Fiss.    16   with    2< 


14  ARCHITECTURE    OP    THE    BRAIN. 

In  general  contour  and  markings  the  lateral  halves  of  the 
cerebrum  are  alike,  but  upon  closer  inspection,  the  convolu- 
tions and  fibsures  of  one  hemisphere  do  not  correspond  with 
and  17  with  26.  those  of  the  other,  and  in  a  comparison  of  any  number  of 
brains,  there  cannot  be  found  any  exact  resemblance  in  the 
hemispheres  of  the  same  side. 

There  are,  however,  certain  distinct  fissures  and  convolu- 
see  description  of     tious    which  cuable  the    anatomist  to  map    out   the    surface 

hemispherical  ^ 

gaigiion.  of  the  brain,   and  to    define    localities  which  may  be    com- 

pared with  those  of  other  brains.  The  whole  surface  of 
the  brain  is  divided  into  general  regions  which  correspond  to 
and  are  named  after  the  bones  of  the  skull  which  cover  them. 
Thus  we  speak  of  the  frontal,  parietal,  occipital,  temporal, 
temporo-sphenoidal,  orbital  and  insular  regions  of  the  brain, 
and  that  which  lies  in  apposition  with  its  fellow  within  the 
longitudinal  fissure,  as  the  inner  or  fissural  region. 

The  convolutions  upon  the  surface  of  the  cerebrum  will 
be  described  later  on  with  the  hemispherical  ganglion. 

STRUCTURE  OF  THE  CEREBRUM. 

In  a  general  description  of  the  anatomy  of  the  cerebrum, 
it  may  be  said  to  arise  by  two  peduncles,  the  parts  of  which 
are  derived  in  front  from  the  pons  Variolii,  and  behind  from 
the  cerebellum.  Each  peduncle  is  about  five-eighths  of  an 
inch  in  length,  about  one  inch  in  breadth  from  before  back- 
wards, and  about  three-fourths  of  an  inch  in  thickness  in  a 
lateral  direction.  The  peduncles  are  separated  from  each 
other  in  the  median  lines  by  a  thin  layer  of  antero  ■  posterior 
fibres  called  the  raphe. 

One  third  of  the  distance  from  the  posterior  median  line,  on 
the  outer  surface  of  each  crus,  is  a  vertical  depression  leadins; 

Jeniculate  bodies.  '  ^  ° 

Figs,  v-8-9-12-13     upwards  from  the  pons  to  a  tubercle,  the  internal  geniculate 

and  vertical  sec-  J-  -^  '  o 

tions  Nos.  20-21-     'body.      lu  frout  of  this  depression  is  a  broad  band  of  coarse 


Peduncles  of  ce 
brum.  Figs.  2 
8'9-10-S6-27. 


:   of    pedunc 
Figs.   26-27 


THE    CEREBRUM. 


15 


fibres,  the  crusta,  which  is  directed  upwards  aud  back- 
wards to  the  lower  margin  of  the  optic  tract  that 
marks  the  upper  boundary  of  the  cerebral  peduncle.  Behind 
the  vertical  depression  is  an  oblique  tract  of  finer  fibres  hav- 
ing the  same  direction  as  those  of  the  crusta  and  extending 
upwards  to  the  testes,  and  to  a  horizontal  tract  which  is 
directed  outwards  from  the  testes  to  the  internal  geniculate 
body,  the  brachium  posterius  The  oblique  tract  behind  the 
depression  arises  apparently  from  the  pons  Varolii,  but  sub- 
sequently will  be  traced  to  the  anterior  column  of  the  spinal 
cord.  This  tract  is  depressed  below  the  level  of  the 
crusta  and  overlaps  a  large  band  of  horizontal  anterio- 
posterior fibres  derived  from  the  cerebellum,  the  pro- 
cesses e  cerebello  ad  testes  (a  misnomer). 

^\^Q  processus  (a  name  which  we  will  continue  to  use  in  place 
of  the  former)  of  one  side  is  connected  with  that  of  the  other 
along  their  internal  margins  by  the  valve  of  Vieussens  which, 
together  with  the  processes,  forms  the  roof  of  the  fourth  ventri- 
cle. The  crustse  diverge  as  they  pass  upwards  from  the  pons  and 
are  separated  in  front  by  a  wide  interval,  the  interpeduncular 
space.  This  interval  between  the  crustte  in  front  is  triangular 
in  shape,  pointed  below,  and  is  about  a  half  an  inch  in  depth 
above  the  pons.  Two  round  white  eminences,  the  corpoT-a 
albicantia,  are  situated  between  the  peduncles  about  half  an 
inch  in  front  of  the  pons  Varolii.  The  third  nerves 
spring  from  the  inner  margin  of  the  crustse  immedi- 
ately above  the  upper  border  of  the  pons.  The  crustse  are 
about  a  quarter  of  an  inch  in  thickness,  and  the  nervous  mass 
enclosed  and  supported  by  them,  composed  of  numerous 
tracts  and  masses  of  white  and  gray  matter,  is  called  the 
tegmentum.  The  crustte  are  the  motor  tracts  and  expand 
above  bodily  into  the  internal  capsules  of  the  cerebral  heniis- 


;rusta.  Figs.  2-7--8 
9-I0-I1-13  15-21- 
S2-23  37. 


Vertical  depression 
on  the  side  of  the 
peduncle.    Fig.  U. 


stes.bra 
leal   gla 


Figs.  6-1 
14-26-27. 


Figs.  8-9-11-12  13 


9-10-11-12-13  N- 
15-27-28-21*  to  2;j* 


infundibulu 
Fig.  9. 


Crust^E   and    teg- 


16 


ARCHITECTURE    OF   THE   BRAIN. 


Tracts 

turn. 


nternal  capsule 
Figs.  4  to  14,  18  t< 
23,  10*  to  19*. 


internal   capsule. 
Figs,    3  8-18*-19'. 


Triangular  space 
enclosed  by  cor- 
pus callosum  and 
internal  capsule. 
Figs,  8.  16*  to  19*. 


pheres,  passing  directly  through  them  to  reach  the  motor 
areas  above  upon  the  sides  of  the  suiface  of  the  brain.  The 
tegmentum  cojitains  the  sensory  tract,  and,  with  one  excep- 
tion, the  fillet,  its  fibrous  structures  are  interrupted  by  masses 
of  grey  matter  before  entering  the  internal  capsule  to  be  dis- 
tributed to  the  surface  of  the  brain.  In  a  section  of  the 
peduncles  the  tegmentum  consists  of  all  that  portion  of  the 
surface  except  the  divided  tracts  of  the  crustse,  which  are 
situated  on  the  sides  and  the  front  of  the  peduncles. 

The  anatomy  of  the  peduncle  will  be  examined  more  closely 
later,  but  at  present  it  is  necessary  to  mark  the  distinction 
between  the  crusta  and  the  tegmentum,  because  these  divisions 
of  the  crus  cerebri  or  peduncle  are  frequently  referred  to  in 
works  upon  anatomy. 

The  internal  capsule  of  each  hemisphere  is  derived  from 
the  expansion  of  a  crus  or  peduncle  of  the  cerebrum.  The 
fibres  of  the  crus  cerebri  pass  upwards  and  outward 
to  about  the  middle  of  the  hemisphere,  where  they  decussate 
with  the  fibres  of  the  corpus  callosum,  external  to  and  above 
the  outer  border  of  the  lateral  ventricle.  Beyond  the  decus- 
sation of  these  tracts,  which  extends  from  before  backwards 
throughout  the  length  of  the  outer  margin  of  lateral  ventricle, 
the  fibres  of  the  corpus  callosum  and  internal  capsule  inter- 
mingle with  those  of  the  longitudinal  commissures  of  the  hem- 
isphere and  constitute  its  white  substance,  or  the  corona  radiata. 

The  corpus  callosum  is  the  great  transverse  commissure  of 
the  brain.  It  forms  the  roof  the  lateral  ventricles,  and  uniting 
upon  its  sides  with  the  fibres  of  the  internal  capsules,  a 
triangular  space  is  enclosed  containing  the  ventricles  and  the 
internal  basal  ganglia. 

A  vertical  section  across  the  middle  of  the  brain  shows 
the  internal  capsule   below  its  junction  with  the  corpus  cal- 


THE    CEREBRUM.  17 

losum  to  be  in  relation  with  internal  and  external  masses  of 
grey  matter,  the  basal  ganglia.  Those  on  the  inside,  are 
the  caudate  nucleus,  and  below  it  the  thalamus  opticus; 
upon  the  outside  of  the  capsule  are  the  three   divisions  of     Lenticuia,  > 

Figs.  9,  12 

the  lenticular  body,  the  corpus  lenticularis  which  is  bounded 
externally  by  the  external  capsule,  claustrum  and  insula  suc- 
cessively. Above  the  decussation  of  the  internal  capsule 
and  the  corpus  callosum  is  the  white  substance  of  the  brain, 
the  corona  radiata,  composed  of  three  layers  ;  an  ex-  ^a  ers  ot 
ternal  or  sub-con volutional,  a  middle  or  the  layer  of  the  '"l-^^t""'  ^ 
longitudinal  commissures,  and  an  internal  or  capsular  layer 
which  immediately  surrounds  the  ventricle. 

The  mass  of  white  matter  constituting  the  corona  radiata 
is  surrounded  by  a  sheet  of  grey  matter  which  extends  along 
the  surface  of  the  convolutions  and  into  the  depths  of  the 
sulci  upon  the  surface  of  the  cerebrum.  This  lamina  of 
grey  matter  covering  the  hemispheres  constitutes  the  hemis- 
pherical ganglia  and  is  the  seat  of  consciousness,  memory 
and  mind. 

The  foregoing  general  description  has  prepared  us  to  con- 
sider each  part  of  the  cerebrum  more  particularly  as  it  appears 
in  the  order  of  dissection. 


splierioalgan 
n.   Figs.  16  17 


DISSECTION. 


Fig.  3-8. 


By  separating  the  sides  of  the  longitudinal  fissure  between 
the  hemispheres  of  the  cerebrum,  there  is  brought  into  view 
Corpus  caiiosum.  ^  broad  baud  of  transverse  fibres,  the  corpus  callosum,  which 
connects  the  hemispheres.  Enclosing  the  corpus  callosum 
behind,  above  and  in  front  is  a  long  continuous  con- 
volution, the  gyrus  fornicatus,  which  overlaps  it  on  each 
side  as  far  as  the  middle  line.  The  fissure  between  tlie  corpus 
callosum  and  the  gyrus  fornicatus  is  about  five-eights  of  an 
inch  in  depth,  extending  in  a  lateral  direction  from  the  bot- 
tom of  the  longitudinal  fissure,  and  is  sometimes  called  the 
ventricle  of  the  corpus  callosum. 

If  the  convolutions  above  the  corpus  callosum  are  gently 
lifted  and  torn  outward,  they  will  break  externally  from  an 
elevated  crest,  one  on  each  side,  which  is  the  line  of  decussa- 
tion of  the  corpus  callosum  with  the  internal  capsule  as  it 
ascends  from  the  crus  cerebri.  These  crests  extend  longi- 
tudinally along  the  middle  of  the  hemispheres  to  near  their 
extremities,  are  more  elevated  in  the  center  than  at  each  end, 
and  are  more  widely  separated  behind  than  in  front.  The 
crests  project  upwards  as  longitudinal  ridges  that  form  the 
outer  boundaries  of  the  corpus  callosum.  The  upper  surface 
of  the  corpus  callosum  is  concave  from  side  to  side  forming 
a  broad  longitudinal  groove,  or  trough  about  four  inches  in 
length  and  two  inches  wide,  situated  in  the  middle  of  the 
cerebrum. 

External  to  the  corpus  callosum  on  each  side  is  the  white 
substance  of  the  brain,  the  corona  radiata,  divided  in  front 


DISSECTION. 


19 


aii<l  behind  into  two  parts  by  the  anterior  and  the  posterior 
median  fissures.  It  is  fringed  by  a  thin  layer  of  grey  matter 
upon  its  outer  border,  and  the  broken  surface  shows  the 
ends  of  torn  blood  vessels,  the  puncta  vasculosa. 

The  whole  surface  exposed  by  breaking  the  upper  part  of 
the  cerebrum  to  a  level  with  the  corpus  callosum  is  oval  in 
shape,  and  convoluted  on  its  margin  by  fissures.  One  on 
each  side  is  deep,  and  situated  behind  the  middle  of  the 
hemisphere,  the  posterior  extremity  of  the  fissure  of  Sylvius. 
Behind  the  corpus  callosum  is  the  exposed  upper  surface  of 
the  cuueus  lobe  of  the  brain,  the  center  of  vision,  and  the 
convolution  immediately  behind  the  fissure  of  Sylvius  is  the 
center  of  word  memories. 

To  illustrate  the  structure  of  the  corona  I'adiata  a  triangle 
has  been  figured  upon  the  right  side  of  figure  3,  which 
serves  to  elucidate  the  phenomena  of  word  blindness,  word 
deafness,  amnesia  and  aphasia,  also  another  triangle  in  front, 
to  illustrate  cerebral  automatic  action.  The  external  side  of 
the  triangle  represents  the  outermost  layer  of  the  corona 
radiata  which  is  composed  of  fibres  passing  between 
adjacent  lobes  and  convolutions.  These  are  called  the 
internuntial  fibres,  and  in  the  illustration  the  tract  is  repre- 
sented through  which  the  name  is  suggested  by  the  object, 
and  vice  versa,  and  the  fingers  are  set  in  motion  automatically 
by  aural  and  visial  impressions. 

The  internal  and  anterior  sides  of  the  triangle  represent 
the  fibres  of  the  external  longitudinal  commissure  which 
associate  the  memory  centres  behind  with  the  seat  of  the 
intellect  in  the  anterior  lobes,  and  with  the  motor  centres  of 
the  central  region  of  the  brain.  The  former  for  the  produc- 
tion of  conscious  and  rational,  and  the  latter  for  subconscious 
ov  automatic  action.      It  is  easy  to  determine  the  results  pro- 


Puncta 

Fig.; 


Figs. 


ntial  fibres 
3  and   18  tt 


20  ARCHITECTURE    OF    TPIE    ERAIIf. 

duced  u]3on  memory,  mind  and  action  by  the  destruction 
of  a  nerve  centi'e,  or  the  interruption  of  any  of  these  tracts 
by  accident  or  disease. 

The  internal  layer  of  the  corona  radiata  is  that  next  to 
and  including  the  crest  or  decussation  of  the  corpus  callosum 
and  internal  capsule.  This  layer  of  the  corona  lies  close  to 
the  walls  of  the  lateral  ventiicle  previous  to  its  distribution. 
External  to  this  layer,  the  fibres  of  the  several  layers  are 
mingled  into  a  network,  the  formatio  reticularis  of  the  cere- 
brum. The  internal  layer  is  composed  wholly  of  fibres  from 
the  corpus  callosum  and  the  internal  capsule,  and  as  they  pass 
toward  the  sui'face  of  the  brain  are  disposed  in  horizontal 
laminae  between  which  the  fibres  of  the  longitudinal  commis- 
sures are  inserted  in  their  passage  from  before  backwards.  The 
outermost  layer  of  the  corona  radiata  is  a  close  network  of 
fibres  passing  in  all  directions  and  therefore  in  dissection  breaks 
into  short  pieces  immediately  beneath  the  convolutions.  The 
three  layers  of  the  corona  may  with  propriety  be  called, 
from  within  outwards,  the  capsular,  commissural  and  inter- 
nuntial  layers.  These  layers  are  exhibited  in  plate  No.  25 
of  the  vertical  sections. 
Dngitudinai  com-  The  LONGiTUDiisrAL  COMMISSURES. — The  longitudinal  fibres, 
i'or'o'"'comm'ir-  ov  commissures  of  the  hemispheres,  are  probably  scattered 
ferior°of  Vor'X  tlirough  tho  eutlro  mass  of  the  corona,  but  in  some  situations 
p'i'gs'^sT'g'is  to  they  can  be  demonstrated  with  ease  and  the  fibres  separ- 
ated for  long  distances.  A  tract  running  parallel  with  the 
bottom  of  the  fissure  of  Sylvius,  beneath  the  insula,  is  of 
Mernai  ion"itu-  cousiderablc  size,  and  is  called  the  external  longitudinal 
commissure.  This  commissure  is  represented  in  the  triangle 
just  described,  and  terminates  in  the  internal  capsule  in  front 
of  the  lenticular  body.  Another  commisui-e  is  situated  in 
the  gyrus  fornicatus  upon  the  inner  side  of   the   crest  and 


sure.     Figs.    19 
20  21. 


DISSECTION. 


21 


resting  within  the  outer  margin  of  the  corpus  callosum.  It 
is  the  superior  longitudinal  commissure,  or  the  commissure  of 
the  gyrus  fornicatus. 

The  raphe  and  stbije  longitudinales. — In  the  middle  line 
upon  the  upper  surface  of  the  corpus  callosum  is  a  slight 
linear  longitudinal  depression,  the  raphe,  and  upon  each 
side,  and  parallel  to  it,  are  two  longitudinal  white  lines, 
the  striae  longitudinales,  or  the  nerves  of  Lancisi.  The 
anterior  fibres  of  the  corpus  callosum  are  arched  forward  into 
the  frontal  lobe,  the  middle  fibres  are  transverse,  and  the 
posterior  form  a  broad  arch  behind  and  are  directed  back- 
wards beneath  the  posterior  cornua  of  the  lateral  ventri- 
cles to  be  distributed  to  the  occipital,  basalar  and  temporal 
convolutions.  The  fibres  of  the  corpus  callosum  decussate 
continuously  with  those  of  the  internal  capsule  above  the 
outer  margin  of  the  lateral  ventricle  and  the  roof  of  the  pos- 
terior cornu,  forming  the  crest.  The  posterior  margin  of  the 
corpus  callosum  is  thick,  is  inverted  beneath  the  posterior 
edge  of  the  fornix,  to  which  it  is  attached  and  is  called  the 
splenium. 

The  splenium  forms  a  part  of  the  upper  boundary  of  the 
intraventricular  portion  of  the  transverse  fissure  of  Bechat. 

The  anterior  margin  of  the  corpus  callosum  is  arched 
downwards  to  the  base  of  the  brain,  where  it  divides  into 
two  peduncles  that  diverge  outward  obli(|uely  across  the 
anterior  perforated  spaces  of  opposite  hemispheres  to  termin- 
ate in  the  anterior  part  of  the  temporal  lobe  upon  each  side. 
At  their  angle  of  divergence  they  bound  tlie  lamina  cinerea 
in  front.  The  downward  deflection  of  the  corpus  callosum  is 
called  its  genu  or  knee. 

A  vertical  section  of  the  corpus  callosum  shows  that  it  is 
about    double    in    thickness    in   front   and    behind    than   in 


Superior  1 
dinal  comr 
Figs.  3  S3. 


Raphe  and 
longitudil 
Fig.  3. 


Spleniu 
5-26. 


Anterior  peduncle 
of    corpus    callc 


22 


ARCHITECTURE    OF   THE   BRAIN. 


Septum  lucidum. 
Figs.   4-5-6-8-10- 
2li  (S.L.) 


Lateral  ventricles. 
Fig.  4. 


:ornua  of  the  lat- 
ral  ventricles. 
Fig.  5. 


the  middle,  and  in  separating  its  fibres,  the  inferior  layer 
is  observed  to  be  turned  downward  at  its  lateral  extremi- 
ties into  the  caudate  nucleii,  while  the  upper  fibres  pass 
upward  into  the  crest  on  either  side.  The  under  surface 
of  the  corpus  callosum  forms  the  roof  of  the  lateral  ventri- 
cles and  is  attached  below  along  the  median  line  from  before 
backwards,  behind  to  the  fornix,  and  in  front  to  the  septum 
lucidum.  Its  attachment  to  these  parts  bounds  the  lateral 
ventricles  internally  and  separates  them  from  each  other. 

The  removal  of  the  corpus  callosum  exposes  the  lateral 
ventricles,  except  the  middle  and  posterior  cornua  which  are 
uncovered  by  a  section  of  the  temporal  and  occipital  lobes. 
The  cavities  thus  exposed  together  present  a  broad  depressed 
surface  between  the  internal  capsules.  These  project  upward 
and  outward,  and  form  its  outer  boundries  on  each  side  for 
two-thirds  of  the  distance  in  front. 

Projections  of  the  lateral  ventricles  extend  into  the  anter- 
ior, middle  and  posterior  lobes  of  the  cerebrum,  and  are  called 
the  anterior,  middle  and  posterior  cornua  of  the  lateral  ventri- 
cles. The  anterior  cornua  are  directed  forward  and  outward, 
the  middle  backwards,  outwards,  downward,  forward  and  in- 
ward, encircling  the  crura  of  the  cerebrum  and  upon  the  floor  of 
each  is  a  rounded  longitudinal  eminence,  the  hippocampus 
major  which  terminates  below  in  a  broad  convoluted  extremity, 
the  pes  hippocampi.  The  posterior  cornu  is  directed  outward, 
downward,  backward  and  inward,  and  projecting  from  its  in- 
ternal wall  is  a  longitudinal  eminence,  the  hippocampus  minor. 
An  oval  eminence  is  situated  externally  at  the  junction  of  the 
middle  and  posterior  cornua  and  is  called  the  pes  accessorius,  or 
eminentia  collateralis.  Behind  the  reflection  of  the  internal 
capsule,  as  it  bends  downward  into  the  roof  of  the  middle 
cornu,  is  a  broad  groove,  directed  outwards  and  downwards, 


DISSECTION. 


23 


Foramen  of  Mom 
Figs.  4-5. 


which  is  the  common  communication  between  the  middle  and 
posterior  cornua  with  the  body  of  the  hxteral  ventricle. 

The  parts  seen  upon  the  floor  of  a  lateral  ventricle,  from 
before  backwards,  are  the  caudate  nucleus,  the  ta3aia  semi- 
cii'cularis,  a  poi'tion  of  the  thalamus  opticus,  the  choroid 
plexus,  corpus  fimbriatum  and  the  fornix.  Between  the 
anterior  pillars  of  tlie  fornix  and  the  anterior  extremity  of 
the  thalamus  is  an  oval  opening  through  which  the  lateral 
ventricle  communicates  with  the  third  ventricle,  and  with 
the  lateral  ventricle  of  the  opposite  side.  This  opening 
transmits  the  choroid  plexus  of  one  ventricle  to  be  contin- 
uous with  those  of  the  others,  and  is  called  the  foramen 
of  Monro.  Extending  backwards  from  the  foi'amen  of 
Monro,  beneath  the  corpus  fimbriatum  or  edge  of  the  fornix, 
as  far  as  the  apex  of  the  middle  cornu  of  the  lateral  ventri- 
cle, is  a  narrow  fissure  which  transmits  the  velum  interposi- 
tum  to  the  lateral  ventricle.  Tliis  fissure  is  called  the  fissure 
of  Bichat,  and  is  the  ventricular  termination  of  the  great 
transverse  fissure. 

The  fornix  is  a  triangular  layer  of  longitudinal  white 
fibres,  with  its  apex  directed  forward  and  its  base  attached 
behind  to  the  posterior  extremity  of  the  corpus  callosum. 
Its  anterior  extremity  divides  into  two  rounded  cords,  one  on 
each  side,  which  descend  in  front  of  the  thalamii  optici  to 
the  base  of  the  brain,  and  obliquely  backward  to  the  cor- 
pora albicautia  in  the  interpeduncular  space,  and  fi-om  these 
latter  are  tracts  of  white  fibres  passing  outward  to  the  internal 
capsules. 

The  apex  of  the  fornix  is  continued  forward  to  the 
genu   of    the    corpus    callosum    in   the    median   line,    by   a     septum  uindum. 

^  _  .  Figs.  4-5-6  8-26. 

thin  membrane,  the.  septum  lucidum.  This  membrane 
fills  up  the  interval  between  the  fornix    and   the    genu    of 


Fissure  of  Bichat 
Figs.  4-5. 


24 


AECHITECTUEE    OF   THE    BRAIN. 


Fifth  ventri 

cle. 

Figs.  4-8. 

Genu  of  the 

internal 

capsule. 

Figs. 

4- 

Corpus  fimbriatum 
and  posterior  pil- 
lars  of    fornix. 
Figs.  4-5. 


Ungual  convolii 
tion.     Fig.  IT. 


Foramen  Monro. 


the  corpus  callosum  dividing  the  lateral  ventricles  from 
each  other.  The  fibres  of  the  septum  lucidum  pass  in 
a  longitudinal  direction  from  the  fornix  to  the  corpus  callos- 
um. The  septum  is  composed  of  two  layers,  side  by  side, 
enclosing  a  vertical  slit,  the  fifth  ventricle.  The  posterior 
angles  of  the  fornix  are  extended  outward,  backward,  and 
downward  along  the  broad  groove  behind  the  arch  or  genu  of 
■the  internal  capsule,  to  be  continuous  with  the  layer  of  white 
fibi'es  which  cover  the  floor  of  the  middle  and  posterior 
cornua.  These  extensions  are  called  its  posterior  pillars, 
each  pillar  apparently  dividing  to  form  the  hippocampus 
major  and  minor  of  the  same  side.  The  edge  of  the  fornix 
is  called  the  corpus  fimbriatum,  and  rests  upon  the  thalamus 
opticus.  It  extends  behind  the  posterior  extremity  of  the 
thalamus  downward  along  the  internal  margin  of  the  floor  of 
the  middle  cornu  and  terminates  in  the  apex  of  the  ungual 
convolution. 

The  choroid  plexus  is  a  capillary  network  lying  upon  the 
thalamus  and  attached  to  the  edge  of  the  velum  interpositum, 
from  which  it  receives  the  blood  vessels  that  supply  it.  It 
extends  from  the  foramen  of  Monro  in  front  over  the 
thalamus  opticus  into  the  middle  cornu  of  the  lateral  ventri- 
cle. It  lies  parallel  with  the  fissure  of  Bichat  and  the  corpus 
fimbriatum  to  their  lower  extremities,  which  terminate  at  the 
apex  of  the  middle  cornu.  The  choroid  plexuses  of  the 
lateral  ventricles  and  those  of  the  third  ventricle  are  con- 
nected through  the  foramina  of  Monro. 

The  fornix  forms  the  roof  the  third  ventricle.  If  it  is 
divided  transversely  and  its  parts  reflected,  its  anterior 
pillars  will  be  seen  descending  in  front  as  two  rounded  cords; 
and  upon  the  under  surface  of  its  posterior  part,  crossing  in 
lateral  direction,  are  several  trausv^erse  stride  called  the  lyra. 


DISSECTION. 


25 


These  Jatter  are  fibres  of  the  corpus  callosum  crossing  in  a 
transverse  direction  beneath  the  attachment  of  the  posterior 
margin  of  the  fornix  to  that  of  the  corpus  callosum. 

Beneath  the  fornix,  and  exposed  by  its  removal,  is  a  pro- 
cess of  pia  mater  extending  into  the  ventricles  of  the  brain, 
and  called  the  velum  interpositum  on  account  of  its  being 
interposed  between  the  fornix  and  the  third  ventricle,  which 
is  beneath  it.  The  velum  interpositum  is  triangular  in  shape, 
corresponding  to  the  under  surface  of  the  fornix,  with  which 
it  is  in  contact.  The  velum  contains  numerous  blood  vessels 
which  supply  the  choroid  plexuses.  Near  its  centre,  side 
by  side,  are  two  large  veins,  the  vena  Galeni,  which  receive 
blood  from  the  venae  corpora  striata  and  convey  it  to  the 
straight  sinus,  at  the  junction  of  the  falx  cerebri  and  tentor- 
um  cerebelli.  Suspended  along  the  middle  line  upon  the 
under  surface  of  the  velum  are  two  fringes,  the  choroid 
plexuses  of  the  third  ventricle,  which  are  continuous  with 
those  of  the  lateral  ventricles  at  the  foramina  Monro.  The 
velum  is  derived  from  the  pia  mater  covering  the  occipital 
and  temporal  lobes  of  the  brain.  It  is  admitted  into  the  third 
ventricle  beneath  the  posterior  border  of  the  corpus  callosum, 
and  passing  forward  under  the  fornix,  beneath  its  lateral  mar- 
gins, it  extends  into  the  lateral  ventricles  through  the  fissures  of 
Bichat.  At  the  outer  sides  of  the  cruri  cerebri,  the  pia  mater 
passes  directly  from  the  under  surface  of  the  brain  into  the 
middle  cornua  of  the  lateral  ventricles  upon  each  side.  This 
membrane  embraces  the  pineal  body,  and  the  latter  may  be 
torn  off  by  its  careless  removal.  The  parts  exposed  by 
its  removal  are,  the  cavity  of  the  third  ventricle,  pineal 
body,  optic  lobes  and  the  thalamus.  These,  together  with 
the  basal  ganglia  and  internal  capsule,  will  now  be  described 
together,  in  order  that  their  relations  may  be  more  clearly 


directly 
lateral 


surface    of    t  h  ^ 


Figs.  5-17 


xposed  by 
jmoval  of 
lum.  Fig.  0. 


!tion   repre- 
ed  by  higs. 


26  ARCHITECTURE    OF   THE   BRAIN. 

understood.  The  removal  of  the  cerebellum,  as  seen  in  Fig. 
8,  is  advantageous  to  this  dissection,  as  the  parts  above  men- 
tioned are  then  seen  in  connection  with  those  below. 

In  general,  this  dissection  presents  a  median  longitudinal 

^"''  depression,  and  two  lateral  masses,  one  on  eacli  side.     In  the 

middle  line,  between  the  lateral  masses,  is  a  longitudinal 

cleft,  the  third  ventricle.     The  third  ventricle  is  one  and  half 

an  incli  in  length,  extends  vertically  to  the  base  of  the  brain, 

Floor  of  third  ven-     ^^]lere  its  floor  is  formed  by  the  parts  contained  in  the  inter- 

tricle.     Fig.  7-9.  •'  ■>■ 

peduncular  space,  including  the  lamina  cinerea,  optic  commis- 
sure and  tuber  cinereum.  Communicating  with  the  ventricle 
below  is  a  canal  leading  to  the  pituitary  body,  the  infundi- 
bulum.  The  pillars  of  the  fornix  descend  in  the  anterior 
extremity  of  the  third  ventricle.  By  separating  the  anterior 
Anterior  commis-      jiillars  of  the  forulx  the  middle  portion  of  the  anterior  com- 

snre.     Figs.  6-13- 

14-21-23  23-14*-  mlssurc  is  exposed,  and  is  seen  crossing  the  anterior  wall  of 
the  ventricle  in  front  of  them.  The  anterior  commissure  of 
the  third  ventricle  is  directed  outward  and  backward  on  each 
side  to  the  extremity  of  the  inferior  ramus  of  the  internal 
capsule  of  the  hemisphere,  its  extremities  terminating  in 
the  temporal  lobes.  It  is  supposed  to  be  the  commissure 
of  the  centres  of  smell  and  taste.  The  internal  surfaces 
of  the  thalami  form  the  lateral  walls  of  the  third  ventricle. 
Crossing  its  middle,  uniting  the  central  part  of  one  thalamus 
wilh  that  of  the  other,  is  a  broad  gray  commissure,  the  mid- 
dle or  gray  commissure  of  the  third  ventricle.  The  ventricle 
is  pointed  behind,  and  is  continuous  with  a  canal  which  passes 
backwards  be^ieath  another  transverse  band  of  white  fibres, 
the  posterior  commissure  of  the  third  ventricle.  The  canal 
just  mentioned  leads  downwards  and  backwards,  beneath  the 
posterior  commissure  and  the  commissure  of  the  corpora 
quadrigemiua  and  valve  of  Vieussens,  to  communicate  with 


Third  ventricle 


'-33  33. 


Ileal    Kland    and 
pillars.    Figs.  6-». 


DISSECTION.  27 

the  fourth  ventricle.     This  canal  is  called  the  aqueduct  of 
Sylvius,  or  the  iter  e  tertio  ad  quartern  ventriculum,  or,  for 
short,  the  iter.     Extending  from  the  anterior  pillars  of  the     The  iter.  Figs.  215- 
fornix  forward  to  the  genu  of  the  corpus  callosum,  and  sep- 
arating the  lateral  ventricles,  is  the  septum  lucidum. 

Behind  the  posterior  extremity  of  the  ventricle,  and 
above  its  posterior  commisure,  is  a  small  globular  body  some- 
what elongated  from  before  backwards,  the  pineal  gland. 
Two  delicate  white  tracts  extend  forward  from  the  anterior 
extremity  of  the  pineal  gland,  one  on  each  side,  upon  the 
lateral  margins  of  the  third  ventricle,  they  are  the  anterior 
pillars  of  the  pineal  gland  and  mark  the  division  between  the 
superior  and  internal  surfaces  of  the  thalamus.  These  tracts  are 
lost  in  front  of  the  anterior  extremity  of  the  thalamus,  where 
they  are  in  conjunction  with  the  descending  anterior  pillars 
of  the  fornix.  The  anterior  extremity  of  the  pineal  gland  is 
attached  to  the  upper  surface  of  the  posterior  commissure  of 
the  third  ventricle  by  a  delicate  membrane,  whose  lateral 
margins  are  thickened  and  called  the  posterior  pillars  of  the 
pineal  gland.  The  posterior  margin  and  sides  of  the  pineal 
gland  are  free,  and  it  rests  above,  in  front  of,  and  between 
the  anterior  tubercles  of  the  corpora  quadrigemina. 

The  corpora  quadrigemina  or  optic  tubercles  are  four 
small  bodies  placed  above  and  between  the  cruri  cerebri,  and 
in  the  interval  between  the  posterior  extremities  of  the  thalami 
optici.  They  are  enclosed  behind  by  a  notch  upon  the 
anterior  part  of  the  cerebellum  the  incisura  anterior.  The 
corpora  quadrigemina  are  in  pairs,  an  anterior  pair,  the  nates, 
and  a  posterior  pair,  the  testes.  The  tubercles  of  each  pair 
are  placed  one  on  either  side  of  the  median  line  and  are  connect- 
ed by  a  commissure.Directed  obliquely  outward  and  forward 
from  the  nates  and  the  testes,  on  either  siile,  are  two  bands 


Corpora    quadrige 


28  ARCHITECTUEE   OF   THE    BRAIN. 

^'9-13-H  ^'^^''^^'  of  white  fibres,  the  brachia,anteriiis  and  posterius,  the  former 
being  connected  with  the  nates,  and  the  latter  with  the  testes. 
These  tracts  are  the  external  margins  of  the  horizontal  layers 
of  fibres  which  pass  from  the  corpora  quadrigemina,  beneath 
the  posterior  extremity  of  the  thalamus,  to  the  internal  capsule. 
They  are  also  connected  with  the  posterior  extremities  of  the 
optic  tract  and  geniculate  bodies,  the  brachium  anterior  with 
the  corjous  geniculatum  externum  and  the  brachium  posteri 
with  the  corpus  geniculatum  internum.  Behind  the  corpora 
cpiadrigimina,  and  covered  by  the  cerebellum,  are  two  broad  and 
rounded  cords,  one  on  each  side,  which  ascend  from  the  hilus 
of  the  cerebellum  and  are  the  processes,  or  the  superior 
peduncles  of  the  cerebellum.  These  are  united  along  their 
inner  margins  by  a  thin  translucent  membrane,  which  is  de- 
pressed upon  its  upper  surface,  and  is  called  the  valve  of 

Processes  and     Vlcussens.     Tlic  valvc  Is  polntcd  at  its  anterior  extremity 

valve    of     Vieus-  -*■  */ 

ms  26^3oV^^"     ■^liich  projects  upwards  between  the  testes,  and  is  elevated 
above  the  general  surface.   On  each  side  of  its  anterior  extrem- 
ity are  the  apparent  origins  of  the  fourth  nerves.      The  under 
surface  of  the  valve  and  of  the  processes  form  the  roof  of  the 
Superior  and  infer-     fourth  veutriclc.     Tho   supcrlor   vermiform    process    of    the 

processes  of  cere-     cerebcllum  rcsts  upon  the  valve  of  Vieussens  and  the  infer. 

30-31.  ior  vermifoi'm  process  is  beneath  it  in  the  fourth  ventricle. 

Upon  the  outer  surface  of  each  processus  at  its  anterior  part, 
crossing  it  obliquely  in  an  upward  direction,  is  a  band  of 
fibres  parallel  to  those  of  the  crusta  from  which  it  is  divided 
by  the  sharp  vertrical  furrow  previously  mentioned.  This 
band  of  fibres  terminates  above  in  the  testes  and  brachium  pos- 
terior, and  below  it  is  continuous  with  the  fundamental  root 
zone  of  the  spinal  cord. 

At  the  upper  extremity  oi  the  depression  between  the 

Corpus   genicula-  '^  '-  •'  ■■■ 

turn  internum,       crusta  aud  the  tract  iust  mentioned  is  a  tubercle,  which  is 

Figs.  7  8-9.  ■>  ' 


Figs.  13-14. 


8  9-10,    10*  to  18*. 


DISSECTION.  29 

connected  behind  with  the  brachinm  posterius,  and  in  front 
with  the  lower  division  of  the  optic  tract,  and  is  called  tlie 
corpus  geniculatum  internum.    External  and  above  the  corpus 
geniculatum  internum,  upon  the  outer  division  of  the  extrem- 
ity of  the  optic  tract,  is  an  elevation,  the  corpus  geniculatum     corpus  genicuia 
externum.   These  bodies  are  apparently  the  outer  terminations       '''S"-  "-^  '■•• 
of  the  brachia,  but,  as  before  stated,  the  major  part  of  the 
fibers  of  the  brachia  passes  beneath  the  thalamus  and   optic    connection  of  t 
tract  to  the  internal  capsule.  int'lniTi  "Ipsuie 

The  basal  ganglia: — Upon  each  side  of  the  third  ventricle, 
resting  upon  the  upj)er  extremities  of  the  peduncles  or  cruri 
cerebri,  are  two  large  masses  of  gray  matter,  one  on  each  side, 
the  basal  ganglia  of  the  cerebum.  Each  mass  is  composed  of 
three  large  ganglia,  two  of  which  are  internal,  and  one  exter- 
nal to  a  broad  and  thick  layer  of  white  fibres,  the  internal 
capsule.  The  capsule  is  seen  projecting  above,  from  between 
the  external  and  internal  ganglia,  as  an  elevated  tract  com- 
posed of  transverse  lamina  or  bundles  of  fibres.  The  fibres 
of  the  antei'ior  portion  of  either  internal  capsule  are  directed     Distribution  of  the 

internal    capsule. 

forward  toward  the  anterior  lobe  of  the  cerebrum,  the  middle       Figs.  7-9-13. 
fibres  upwards  to  the  parietal  region,  and  the  posterior  backwards 
and  outwards  into  the  occipital  and  temporal  lobes  of  the  brain. 
The  internal  capsule  radiates  like  the  pinna  of  the  ear,  an 
interspace  being  left  opposite  the  anterior  perforated    space     interspace  in  cap- 
between  the  frontal  and  temporal  lobes  of  the  hemisphere.        i8to2o.''' 
In  consequence  of  this  disposition  of  the  fibres  of  the  capsule, 
it  encloses  a  conical  concavity,  open  externally,  which  is  filled 
by  a  mass  of  gray  matter,  the  lenticular  nucleus,   or  external     Lenticular  nucleus 
basal  p-anojlion.  fumei.   Figs.  7- 

At  its  posterior  part,  the  internal  capsule  sweeps  around  an 
•abrupt  curve  as  it  descends  to  form  the  roof  of  the  middle 
cornu  of  the  lateral  ventricle.      The  ]-eflected  portion  of  the 


CaudalB  ni 
FiKS.  4 -6- 
11«  (N  C) 


30  ARCHITECTURE    OF    THE    BRAIN. 

capsule  is  distributed  to  the   temporal   lobe  and  its  abrupt 
deflexion  behind  is  called  its  genu. 

The  INTERNAL  BASAL  GANGLIA  : — The  internal  basal  ganglia 
rest  upon  and  are  attached  to  the  internal  surface  of  the 
internal  capsule.  They  are  separated  from  each  other  by  a 
depression,  and  a  narrow  band  of  white  fibres,  the  taenia 
semicircularis.  The  superior  internal  ganglion,  or  caudate 
nucleus,  rests  upon  the  upper  portion  of  the  internal  surface 
of  the  internal  capsule,  and  projects  into  the  floor  of  the  lat- 
eral ventricle.  Its  anterior  portion,  or  body,  is  large,  and 
occupies  the  anterior  cornu  of  the  lateral  ventricle.  Tlie  pos- 
terior part  or  tail  of  the  caudate  nucleus  gradually  tapers 
from  the  body  in  front  to  form  a  narrow  elevation  which 
runs  along  the  outer  margin  of  the  lateral  ventricle,  and, 
bending  beneath  the  genu  of  the  internal  capsule,  enters  the 
roof  of  the  middle  cornu,  at  the  end  of  which  it  terminates 
in  a  bulbous  extremity. 

The  taenia  semicircularis  is  a  narrow  band  of  white  fibres 
at  the  bottom  of  a  depression  which  separates  the  caudate 
nucleus  from  the  thalamus  opticus.  It  extends  along  the 
whole  length  of  the  lower  margin  of  the  caudate  nucleus. 
Beginning  in  front  immediately  anterior  to  the  anterior  pillars 
of  the  fornix  as  a  broad  surface,  it  extends  backward  as  a 
narrow  band  which  terminates  below  at  the  end  of  the  middle 
cornu  and  is  attached  to  the  apex  of  the  ungual  convolution. 

The  taenia  semicircularis  in  the  floor  of  the  lateral  ven- 
Fig.\  ^"^  ^""'  tricle  has  the  appearance  of  a  narrow  band  of  white  fibres, 
but,  when  the  caudate  body  is  removed,  it  is  seen  to  be  the 
margin  of  a  tract  of  fibres  which  is  derived  from  slips  emerg- 
ing from  between  the  lamina  of  the  internal  capsule  to 
increase  its  volume  as  it  passes  forward  beneath  the  caudate 
nucleus. 


Derivatii 

Lefl 


DISSECTIOT^. 


31 


The  thalamus  opticus: — The  inferior  internal  ganglion,  oi' 
thalamus  opticus,  in  general  outline  is  fusiform  in  shape.  Its 
body  is  somewhat  elongated,  and  a  transverse  section  shows 
that  it  is  prismatic.  Its  upper  surface  is  divided  into  two 
portions  by  an  oblique  depression  which  begins  in  front 
behind  the  anterior  pillar  of  the  fornix,  and  extends  backward 
and  outward  to  its  external  margin  at  the  genu  of  the  internal 
capsule.  The  surface  above  and  external  to  this  depression 
forms  a  part  of  the  floor  of  the  lateral  ventricle.  The  por- 
tion below  or  internal  to  the  depression  is  covered  by  the 
fornix,  and  is  continuous  behind  and  below  the  crus  cerebii 
with  the  outer  division  of  the  optic  tract.  The  internal  sur- 
face of  the  thalamus  forms  the  lateral  wall  of  the  third  ven- 
tricle, and  in  the  middle  of  the  ventricle,  is  united  to  the  thal- 
amus of  the  opposite  side  by  the  middle  or  gray  commissure 
of  the  third  ventricle.  The  inferior  surface  of  the  thalamus 
looks  outwards  and  downwards  and  is  attached  to  the  internal 
capsule  to  which  it  gives  off  a  great  mass  of  fibres,  before 
and  behind,  forming  the  anterior  and  the  posterior  divis- 
ions of  the  internal  capsule.  A  tract  of  longitudinal  fibres, 
called  the  fillet,  lies  external  and  beneath  the  lower  portion 
of  the  inferior  surface  of  the  thalamus. 

Upon  closer  inspection  the  thalamus  will  be  seen  to  con- 
sist of  several  smaller  masses,  more  or  less  similar  in  shape 
to  that  of  the  caudate  nucleus.  The  anterior  extremities  of 
these  masses,  composing  the  thalamus,  are  large,  and  their 
posterior  portions  taper  into  tracts,  which  pass  backwards 
around  the  genu  of  the  internal  capsule.  These  bodies  are, 
from  within  outwards:  first,  a  small  body  situated  at  the  side 
of  the  posterior  extremity  of  the  third  ventricle,  between  the 
pineal  gland  and  the  posterior  extremity  of  the  thalamus, 
and  connected  with  the  anterior  pillar  of  the  pineal  gland, 


.n  of  the  thai- 
■  to  the  fillet. 
10-13-21-22- 


the  Thala 
Fig.  6. 


32  ARCHITECTURE    OF    THE    BRAIN. 

called  the  pison  (pea).     This  body  has  no  posterior  exten- 

2.  Thepuivinar.     sioQ.       Secoiid,   a  fusiform  body,    beginning  in  front  by  a 

pointed  extremity  above  the  middle  commissure,  and  rapidly 
enlarging  forms  a  prominence  upon  the  posterior  portion 
of  the  thalamus,  after  which  it  gradually  contracts  and  is 
continuous  with  the  external  geniculate  body  and  the  superior 
division  of  the  02Dtic  tract.     Tliis  body  is  called  the  pulvinar 

3.  Thetubercu-      aud  Is  probablv  the  vlsual  centre  of  the  thalamus.     Third,  a 

lumthalami.  .  . 

prominence  upon  the  anterior  extremity  of  the  thalamus,  in 
front  of  the  apex  of  the  pulvinar,  behind  the  anterior  pillars 
of  the  fornix  and  above  the  foramen  Monro,  called  the  tuber- 
culum  of  the  thalamus.  Extending  backward  and  slightly 
outward  from  this  tubercle  is  a  tract  of  white  fibres  which 
follows  the  groove,  before  mentioned,  on  the  upper  sur- 
face of  the  thalamus  as  far  as  the  genu  of  the  internal  cap- 
sule, among  the  fibres  of  which  it  is  lost.  The  tuberculum 
thalami  is  supposed  to  be  the  basal  centre  of  taste  and  smell. 

Thefusiformis.  Fourtli,  extemal  to  the  tuberculum  and  the  tract  just  de- 
scribed, and  more  distinctly  seen  if  the  latter  is  I'emoved,  is  the 
largest  body  composing  the  thalamus.  It  is  broad  in  the 
centre,  pointed  at  each  extremity,  fusiform  in  shape,  reaching 
across  the  upper  surface  of  the  internal  capsule,  and  separ- 
ated from  the  caudate  nucleus  by  the  t?enia  semicircularis. 
This  body  is  supposed  to  be  the  thalamic  centre  of  common 
sensation.  Fifth,  underneath  the  central  part  of  the  thala- 
mus, and  imbedded  in  the  tegmentum  of  the  crus  cerebri,  is 

Fig"''"nT3' 14-  a  round  body,  somewhat  larger  than  a  pea,  called  the  sub- 
thalmic  ganglion,  or  red  nucleus.  This  body  does  not  prop- 
erly belong  to  the  thalamus,  but  is  closely  associated  with 
it.  It  is  the  termination  of  the  anterior  extremity  of  the 
processus,  or  supeiior  peduncle  of  the  cerebellum,  and 
from   it   are   distributed    fibres    which    pass   to   the    bodies 


Subthalmic 
;anglion  or  red 
lucleus   of   the 


15-19*-20*, 


DISSECTION.  33 

composing  the  thalamus  under  which  it  lies.     The  red  nucleus     pig.  ,5. 
is  in  relation  externally  with  the  iillet,  and  internally  with  the 
continuation  of  the  gray  matter  which  surrounds  the  iter  and 
lines  the  wall  of  the  third  ventricle. 

The  external  basal  ganglion: — The  gray  matter  external     External  basai  o, 

°    _    -^  lenticular  gantjli 

to  the  internal  capsule,  and  enclosed  by  its  funnel  shaped  °°-  Figs- 9-12-20 
concavity,  is  the  lenticular  ganglion,  so  called  because  its 
parts  are  disposed  in  lenticular  layers.  Its  layers  are  super- 
imposed and  separated  from  each  other  by  laminae  of  white 
fibres,  called  capsules.  A  transverse  section  of  the  entire 
mass  of  the  lenticular  body,  including  the  parietal  and  tem- 
poral portions  of  the  internal  capsule,  is  triangular.  The 
apex  of  the  triangle  is  directed  downward  and  inward,  and  its 
base  is  opposed  to  that  of  the  insula.  It  will  be  seen  that 
the  lenticular  nucleus  is  bounded  above  and  below  by  the 
internal  capsule  and  is  in  three  layers  or  parts.  The  outer  sur-     Transverse  section 

'^  ''  r  ^f  j,,g  lenticuarl 

face  of  each  layer  is  convex  and  composed  mostly  of  gray       nucleus.  Figs  n* 

matter,  while  the  inner  portion  of  each  section  is  traversed  by 

numerous  white  tracts  for  some  distance  from  the  septum  or 

capsule.     The   three   bodies   which   comprise  the  lenticular 

nucleus  increase  in  size  and  thickness  from  within  outwards. 

The  innermost  is  a  conical  wedge  spreading  the  fibres  of  the 

internal  capsule  at  the  bottom  of  its  funnel  shaped  concavity. 

The  inner  and  middle  portions  are  together  called  the  globus 

pallidus,  on  account  of  being  much  paler  in  color  than  the 

outermost,    which  is   called   the   putamen.     Externally   the 

outer  body  or  portion  of  the  lenticular  nucleus  is  covered  by 

a  thick  layer  of  radiating  white  fibres  which  diverge  from 

below  upwards. 

The  layer  of  diverging  fibres  external  to  and  overlying 

^       °  J         »         External    capsule. 

the  lenticular  body,  forming  the  external  capsule,  is  thicker       Figs. --9 19  io»  10 
above  than  below,  and  is  united  with  the  outer  surface  of  the 


34 


ARCHITECTURE    OF    THE    BRAIN. 


u,n.      Figs. 
.  1«*  (c  1,- 


oiitward.  Figs.  5- 
1d*-16*,  betweeu 
(IC  and  IC). 


3rusta  and  tegme 
turn.     Fig.  :)2. 


internal  capsule  above  and  along  the  upper  margin  of  the 
lenticular  nucleus  The  external  capsule  is  covered  upon  its 
outer  surface  by  a  thin  layer  of  gray  matter  which  is  thicker 
below  than  above,  and  is  called  the  claustrum,  (a  wall,) 
external  to  which  is  the  subinsular  layer  of  white  matter,  and 
the  insula.  These  parts  therefore  enclosed  by  the  funnel 
shaped  whorl  of  the  fibres  of  the  internal  capsule  are,  from 
within  outward,  the  three  divisions  of  the  lenticular  nucleus, 
the  external  capsule,  claustrum  and  tbe  white  and  gray 
matter  of  the  insula,  the  latter  being  enclosed  in  the  Y 
shaped  expansion  of  the  bottom  of  the  fissure  of  Sylvius. 

The  internal  capsule  will  be  studied  in  detail  subsequent 
to  the  description  of  those  parts  below  whicb  enter  into  its 
formation.  It  is  sufficient  at  this  time  to  remember  its 
shape,  its  relations  to  the  basal  ganglia  and  that  fibres  from 
these  ganglia  contribute  to  swell  its  volume. 

Because  of  the  funnel  shape  of  the  internal  capsule,  a 
horizontal  section  of  the  brain,  as  generally  represented  in 
diagram,  shows  an  anterior  and  a  posterior  arm,  and  locates 
the  motor  portion  of  the  capsule  behind  the  knee  in  the 
anterior  part  of  the  posterior  arm. 

The  hemispherical  ganglion  and  lateral  dissections  of  it 
will  be  described  after  its  internal  anatomy  has  been  traced 
in  a  longitudinal  direction.  The  crura  cerebri  or  peduncles 
of  the  cerebrum,  as  before  stated,  consist  of  two  portions, 
the  crusta  and  the  tegmentum.  The  crusta  is  a  broad  band 
of  fibres  upon  the  outer  and  anterior  part  of  either  crus  cere- 
bri. The  tegmentum  is  all  that  portion  of  the  peduncle 
behind  and  internal  to  the  crusta.  The  crusta  originates 
entirely  from  the  pons  Varolii,  but  the  tegmentum  is  con- 
nected with  the  cerebellum  and  with  the  posterior  layer  ot 
the  pons  which  includes  the  fillet  and  fasciculi  tei-etes,  and 


DISSECTION.  35 

through  these  with  the  spinal  cord.  The  connections  and  the 
relations  of  the  various  tracts  which  comjDose  the  peduncle  of 
the  cerebrum  will  be  more  clearly  understood  after  the  struc- 
ture of  the  cerebellum  and  the  pons  Varolii  have  been  studied. 
We  will  again  return  to  the  anatomy  of  the  cerebrum  in 
order  to  trace  the  parts  of  the  peduncle  to  their  connections 
with  those  of  the  hemisphere. 


CEREBELLUM. 


;erebellu 
6-7  27  t( 


Superior  and  infer- 


ra   anterior 
posterior. 


Peduncle  ( 
cerebellu 
8  to  l&'A. 


It  will  not  assist  ns  to  the  understanding  of  tlie  architec- 
ture of  the  central  nervous  system  to  enter  into  a  minute 
description  of  the  external  surface  and  shape  of  the  cere- 
bellum. Its  external  appearance  and  the  divisions  of  its  sur- 
face will  be  readily  understood  by  a  study  of  the  plates  in 
this  work.  It  is  sufficient  to  say  that  it  is  composed  of  a 
middle  and  two  lateral  lobes.  The  upper  portion  of  the  mid- 
dle lobe  is  called  the  superior,  and  the  lower  part  the  inferior 
venniform  process  of  tlie  cerebellum.  The  superior  vermi- 
form process  rests  upon  the  upper  surface  of  the  valve  of 
Vieussens,  and  the  inferior  vermiform  process  is  beneath  the 
valve,  and  within  the  fourth  ventricle.  The  lateral  lobes 
project  backwards  and  outwards,  and  are  large  masses  sep- 
arated in  front  by  a  notch,  the  incisura  anterior,  and  behind 
by  a  deep  and  narrow  fissure,  the  incisura  posterior.  In 
front  of  the  lower  surfaces  of  the  lateral  lobes,  beneath  the 
lower  margin  of  the  pons,  are  two  small  lobes,  one  on  each 
side  of  the  medulla  oblongata,  called  the  flocculi. 

The  cerebellum  is  connected  with  the  cerebrum  by  the 
processes  which  are  its  superior  peduncles;  with  the  pons  in 
front  by  its  middle  peduncles;  and  with  the  spinal  cord 
below  by  two  rounded  cordlike  bodies,  the  restiform  bodies, 
or  its  inferior  peduncles. 

A  section  of  the  middle  lobe  of  the  cerebellum  in  the 
median  line  from  before  backward,  exposes  the  fourth  ventri- 
cle.    The  surface  of  the  section  presents  a  beautiful  arbores- 


CEREBELLUM. 


37 


cent  distribution  of  white  matter  radiating  from  the  end  of  a 
lougitudiual  section  of  the  valve  of  Vieussens  the  rami  from 
which  divide  into  small  branches  as  they  approach  the 
surface.  These  subdivide  into  minute  stems  of  white  fibres 
terminating  in  small  leaflets  which  line  the  sides  of  the  deep 
fissures  that  project  inward  from  the  surface  of  the  lobe. 
The  appearance  presented  by  this  section  is  called  tlie  arbor 
vitse. 

A  section  across  a  lateral  lobe,  outward  and  backward, 
shows  within,  a  large  mass  of  white  matter,  an  arbores- 
cent border,  and  imbedded  in  the  anterior  part  of  the  while 
substance  a  convoluted  layer  of  gray  matter  surrounding  a 
portion  of  white  substance  of  irregular  shape.  This  body  is 
called  the  corpus  dentatum  of  the  cerebellum  and  is  its 
sensory  or  internal  basal  ganglion. 

In  a  properly  hardened  cerebellum,  if  the  sides  of  its 
transverse  fissure  are  separated,  and  the  upper  half  gently 
torn  from  the  lower  and  broken  oiF  in  front,  it  will  be  ob- 
served that  the  sui'face  of  either  lobe  will  separate  behind 
and  in  front  over  the  dentate  body,  that  the  fractured 
fibres  are  external  to  this  body,  and  are  those  of  the  middle 
peduncle  of  the  cerebellum. 

The  upper  surface  of  the  dentate  body  ia  elevated  above 
the  remaining  portion  of  the  surface  thus  exposed  upon  the 
inferior  segment,  or  lower  portion  of  the  cerebellum.  This 
surface  presents  numerous  lines  radiating  outward  from  the 
corpus  dentatum,  and  others  directed  inward  and  backward, 
from  the  broken  middle  peduncle  of  the  cerebellum.  The 
fibres  from  these  separate  sources  commingle  to  form  the 
corona  radiata  of  the  cerebellum. 

It  will  be  observed  that  the  processus,  or  superior  pedun- 
cle of  the  cerebellum,  of  either  side  passes  directly  down- 


Figs. 


ate  body. 


of  thecerebellun 
Fig.  Ib'A. 


Figs.    8  9- 


38  ARCHITECTURE    OF    THE    BRAIN. 

ward  and  backward  into  the  centre  of  the  corpus  dentatum, 
entering  its  hilas  upon  the  under  surface.  The  lower  extrem- 
ity of  the  processus,  on  its  outer  side,  is  overlapped  by  a 
tract  of  radiating  iibres  wliich  spring  upward  from  the  inter- 
val between  the  middle  and  superior  peduncles  of  the  cere- 
bellum as  tbey  approach  each  other.  This  tract  emerging 
from  between  the  superior  and  middle  peduncles,  is  the  upper 
extremity  of  the  restiform  body,  or  inferior  peduncle  of  the 
cerebellum,  and  is  distributed,  to  the  upper  surface  of  the 
corpus  dentatum. 

Tlie  attention  is  directed  to  the  fact,  that  the  corpus 
dentatum  is  connected  with  the  superior  and  the  inferior 
peduncles  of  the  cerebellum,  directly  associating  this  body 
with  the  cerebrum  above,  the  spinal  cord  below,  and 
the  cerebellum  behind.  The  middle  peduncle  is  composed 
of  two  distinct  layers  of  fibres,  differing  in  function,  con- 
nected directly  with  the  gray  matter  of  the  surface  of  the 
cerebellum  and  having  no  connection  with  the  corpus  den- 
tatum. 
oniparison  of  the  Thus  it  Is  apparent  that  there  is  an  analogy  between  the 

beiiumtothoseof  structure  of  the  cerebellum  and  that  of  the  cerebrum  and  its 
application  at  this  time  will  assist  us  to  understand  those 
parts  of  the  pons  Varolii  and  medulla  oblongata  which  are 
associated  in  the  comparison. 

The  sheet  of  gray  matter  which  covers  the  surface  of  the 

cerebellum,  and  dips  into  its  fissures,  is  analagous  to  that 

which  covers  the  hemisjiheres   of   the    cerebrum,  and    may 

emisphericaisan-     thercfore  be  called  the  hemispherical   a:anglia  of  the  cere- 

glion  of  the  cere-  ^  &         t> 

bellum.  The  enclosed  mass  of  white  matter,  composed  of 
the  interlacing  fibres  of  the  middle  peduncle  and  the  corpus 
dentatum,  constitute  the  corona  radiata  of  the  cerebellum 
The  corpora  deutata,  associated  with  tlie  sensory  tracts  of  the 


bellu 


CEREBELLUM. 


39 


cerebro  spinal  axis,  correspond  to  the  internal  basal  ganglia 
of  the  cerebrum,  and,  as  we  shall  see  subsequently,  the 
external  basal  ganglia  of  the  cerebellum  are  displaced,  and 
are  located  in  the  pons  Varolii.  The  superficial  layer  of 
the  pons  unites  the  opposite  hemispheres  of  the  cere- 
bellum, and  is  the  analogue  of  the  corpus  callosum  of 
the  cerebrum.  The  deep  layers  of  fibres  of  the  middle 
peduncles  terminate  in  the  gray  matter  of  the  pons  Varolii, 
and  correspond  to  the  motor  tracts  of  the  internal  capsules  of 
the  cerebrum,  and  the  crustse  of  the  crura  cerebri.  The 
superior  and  inferior  peduncles  of  the  cerebellum  are  inter- 
rupted in  their  passage  by  the  corpora  dentata,  thus  they 
coincide  with  the  tegmentum  of  the  crurse  cerebri.  The  direct 
connection  of  the  cerebellum  with  the  spinal  cord,  by  means 
of  the  direct  cerebellar  tract  and  the  arciform  fibres  of  the 
medulla  oblongata,  may  correspond  with  the  fillet  of  the  cere- 
brum, completing  the  analogy  between  these  large  masses 
of  cerebro  spinal  axis.  Taken  together,  the  superior  pedun- 
cle, the  internal  portion  of  the  middle  peduncle,  and  the 
inferior  peduncle  of  the  cerebellum,  strikingly  correspond  to 
the  several  elements  which  enter  into  the  formation  of  the 
internal  capsule  of  the  cerebrum. 

By  the  use  of  the  above  analogy  the  study  of    the  con- 
necting parts  is  made  easy. 


Corpora  dentata, 


Superficial  fibers  of 


Deep  layer,  the 
tor  tract  of  it 


peduncl 
respond  t 


THE  PONS  VAROLII. 


Description  of  the  The  poiis  Varolii  is  a  broad  and  thick  band  of  transverse 


pons  V 


fibres  crossing  in  front  of  the  upper  continuation  of  the 
spinal  cord  and  the  medulla  oblongata,  interrupting  the 
anterior  median  fissure,  and  connecting  the  opposite  hemis- 
pheres of  the  cerebellum.  It  is  about  one  inch  and  a  half 
broad  from  above  dowuAvard,  and  nearly  two  inches  in  a 
lateral  direction.  It  is  contracted  upon  each  side  as  it 
approaches  the  cerebellum,  where  it  forms  the  middle  pedun- 
cles of  that  body.  Its  general  shape  is  oval,  and  its  anterior 
surface  is  convex  in  every  direction.  A  shallow  depression 
crosses  its  surface,  from  above  downward  in  the  median  line, 
called  the  basilar  groove,  which  lodges  the  basilar  artery. 
This  portion  of  the  pons  is  perforated  by  numei'ous  openings 
for  the  passage  of  blood  vessels.  The  upper  margin  of  the . 
pons  is  bounded  in  the  middle  by  the  posterior  perforated 
space  and  laterally  by  the  fibres  of  the  crustse.  The  third  nerves 
arise  from  the  inner  sides  of  the  crustse  above  this  margin. 
Its  lower  margin  is  bounded  in  the  middle  line  by  the  anterior 
median  fissure  and  raphe  of  the  medulla  oblongata,  and  suc- 
cessively on  each  side  of  the  fissure,  from  within  outwards, 
by  the  anterior  pyramid,  olivary  body,  lateral  tract,  and  the 
Figs.  8-26.  restiform  body.     Behind  the  pons  Varolii  is  the  floor  of  the 

'loccuii.  Figs.  7-  fourth  ventricle.  The  flocculi  rest  upon  the  outer  extremities 
of  its  lower  border  in  front  of  the  restiform  bodies.  The 
sixth  nerve  emerges  from  between  the  pyramid  and  the  olive, 
the  seventh-  and  ei2;hth  from  internal  to  the  flocculus  and  resti- 


Fourth  ventricle 


eighth 
Figs.  9^ 


THE   PONS   VAROLII. 


41 


form  body,  and  each  of  these  nerves  is  directed  forward 
beneath  the  lower  border  of  the  pons.  The  fifth  nerve 
emerges  from  the  middle  of  the  anterior  surface  of  the  mid- 
dle peduncle  of  the  cerebellum. 

The  lower  fibres  of  the  superficial  layer  of  the  pons, 
which  form  the  lower  third  of  its  anterior  surface  are  trans- 
verse in  direction,  and  are  overlapped  at  their  outer  extrem- 
ities by  those  from  above  which  arch  downwards  near  their  ter- 
mination. The  upper  transverse  fibres  are  arched  upward  in  the 
middle  and  terminate  in  the  lower  lobes  of  the  cerebellum  on 
each  side.  The  uppermost  fibres  of  the  pons  are  seen  to  proceed 
from  the  posterior  perforated  space,  and  winding  close  to  the 
cms  cerebri  on  each  side  are  directed  backwards  to  enter  the 
cerebellum  above  the  processes.  These  latter  fibres  do  not 
properly  belong  to  the  pons  Varolii,  but  are  derived  from  the 
floor  of  the  fourth  ventricle,  and  passing  forward  through  the 
raphe  connect  the  gray  matter  of  the  fourth  ventricle 
with  the  cerebellum.  They  are  similar  in  function  to  the  rest- 
ifoi'm  body  of  the  medulla  oblongata  and  are  distributed 
to  the  corpus  dentatum  in  conjunction  with  the  inferior  pe- 
duncle of  the  cerebellum.  Other  fibres,  derived  from  the 
floor  of  the  fourth  ventricle,  enter  the  raphe  and  pass  down- 
wards beneath  the  lower  margin  of  the  pons.  These  emerge 
in  front  from  the  anterior  median  fissure  of  the  medulla 
oblongata  and  winding  over  the  pyramid  and  olive,  in  con- 
junction with  the  arciform  fibres,  join  the  restiform  bodies 
to  terminate  in  the  corpus  dentatum  of  the  cerebellum. 
Doubtless,  also,  there  are  associated  with  these,  other  fibres 
that  correspond  to  the  direct  cerebellar  tract  of  the  spinal 
cord,  and  which  will  be  better  understood  after  this  tract 
has  been  described. 


The  uppermost 
iibres  of  the  pons. 
Figs.  9-10. 


Inferior  restiform 
fibres  of  the  floor 
of  the  fourth  ven- 
tricle.   Figs.  9-10. 


Section  of  the  pons 


Plano-concav 
face  of  the 
and    th 
and  lenticula 
section.    Figi 
to  14  26 


42  ARCHITECTURE   OF   THE   BEAEST. 

Structure  of  the  foists  Varolii  : — The  several  layers  of 
which  the  pons  Varolii  is  composed,  will  be  more  easily  under- 
i'trdi'vision°ln"o  stood  by  dividing  it  in  the  median  line  from  before  backward, 
'"°''°'''°"l         into  lateral  halves.      After  the  cerebellum  has  been  removed, 

Figs.  26-3i-3o.  " 

if  the  pons  Varolii  is  torn  in  a  longitudinal  direction  along 
the  floor  of  the  fourth  ventricle  in  its  posterior  median  fissure, 
it  will  separate  into  striated  sui'faces  to  the  depth  of  about  a 
quarter  of  an  inch  in  the  middle  of  the  ventricle,  and  above 
the  pons,  between  the  cruri  cerebri,  it  will  divide  as  far  for- 
ward as  the  posterior  perforated  space,  and  below  to  the 
anterior  median  fissure  of  the  medulla  oblongata.  The 
adjacent  surfaces,  thus  separated,  will  be  seen  to  form  each 
a  plaino- concave  surface,  concave  in  front  and  straight  upon 
its  posterior  margin  along  the  floor  of  the  fourth  ventricle. 
If  the  remaining  portion  of  the  pons  is  now  divided  in  the 
median  line  by  the  knife,  the  pons  will  be  separated  into 
lateral  halves.  The  surface,  presented  by  a  section  of  the 
anterior  portion  of  the  pons,  is  lenticular  in  shape  and  covers 
the  anterior  two-thirds  of  the  whole  surface  thus  exposed. 

It  will  be  observed  that  in  a  division  of  the  pons  Varolii, 
transverse  to  the  fibres  on  its  anterior  surface,  and  longi- 
tudinal to  the  cerebro  spinal  axis,  the  divided  surface  presents 
two  distinct  portions  for  examination ;  an  oval  portion  in 
front  which  is  connected  with  the  anterior  pyramid  of  the 
medulla  oblongata,  and  with  the  crusta  of  the  crus  cerebri ; 
and  behind,  a  plano-concave  surface  of  radiating  fibres,  the 
raphe,  which  separates  the  lateral  halves  of  the  crura  cerebri, 
the  posterior  part  of  the  pons,  and  the  medulla  oblongata. 
Raphe.  Figs.  11  to  1'he  Taphc  is  composed  of  anterio-posterior  fibres,  and  is  an 
important  structure,  because,  within  it  are  the  decussations  of 
the  nerves  of  the  medulla  oblongata  and  the  commissures  of 
the  nerve  centres  situated  in  the  floor  of  the  fourth  ventricle. 


1 4-26  36. 


THE    PONS    VAROLII. 


43 


Upon  each  side  of  the  posterior  margin  of  the  raphe,  upon 
the  floor  of  the  fourth  veutricle,  and  that  of  the  iter,  are  two 
rounded  cords,  the  fasciculi  teretes.  These  are  broad  in  the 
ventricle  below,  narrow  above  in  the  floor  of  the  iter,  and  are 
continuous  in  front  with  the  gray  matter  upon  the  lateral 
walls  of  the  third  ventricle.  These  columns  attend  the  pos- 
terior margin  of  the  raphe  as  far  as  the  floor  of  the  third 
ventricle.  The  superior  margin  of  the  raphe  curves  abruptly 
in  the  floor  of  the  third  ventricle  forward  to  the  base  of 
the  brain  in  front  of  the  corpora  albicantia. 

In  that  part  of  the  raphe  which  separates  the  crura  cere- 
bri is  an  oval  opening  about  the  size  a  split  pea,  around  which 
the  fibres  of  the  raphe  separate  to  form  its  margins.  This 
opening  in  the  raphe  is  filled  by  the  extremity  of  a  tract  of 
broken  fibres  which  ai'e  those  of  the  decussation  of  the  pro- 
cesses, or  superior  peduncles  of  the  cerebellum.  The  fibres 
of  the  processes  pass  beneath  the  fasciculi  teretes,  and 
decussate  within  this  opening  in  the  raphe.  The  pro- 
cessus of  the  opposite  side  crosses  the  raphe  at  this  point  to 
reach  the  red  nucleus  which  is  situated  external  to  the  raphe 
above  the  point  of  decussation.  (The  letters  RN  Figure  26, 
are  placed  over  the  situation  of  the  red  nucleus  which  is 
buried  within  the  tegmentum  of  the  cms  cerebri.)  The 
opening  in  the  raphe,  just  described,  is  above  the  superior 
margin  of  the  pons,  and  in  the  middle  of  that  portion  of  the 
raphe  which  separates  the  cruras  cerebri  from  each  other. 

By  the  removal  of  the  raphe  there  will  be  seen,  behind 
the  pons,  the  margin  of  a  longitudinal  tract  of  white  fibres 
extending  from  the  medulla  oblongata  to  the  crus  cerebri 
above.  This  tract,  is  the  internal  lateral  margin  of  the 
lemniscus  or  fillet,  Avhich  is  separated  from  its  fellow  by  the 
raphe.      This  tract  is  crescent  in  shape,  with   its  concavity 


downward  curve 
of  the  upper  bor- 
der ot  the  raphe 
in  the  floor  of  the 


third 


)val  opening  il 
raphe.  Fig. 
(PTJ. 


Red  nucleus.  Figs. 
10  13  to  15^-19*- 
20*  (RNJ. 


Internal  margin  of 
the  lemniscus  or 
fillet.  Fig.  26  (FT). 


)-postenor 
ction  of  the 
Figs.  11  to 


44  ARCHITECTURE    OF   THE    BRAIN. 

applied  to  the  posterior  convexity  of  the  lenticular  section 
of  the  pons  before  described.  Behind  the  fillet  is  a  layer 
of  gray  matter  which  underlies  the  floor  of  the  fourth  ventri- 
cle, and  constitutes  the  fascicula  teretes. 

The  pons,  therefore,  consists  of  two  distinct  portions ;  an 
anterior  portion  composed  of  transverse  and  longitudinal 
fibres,  the  deep  layer  of  which  is  mixed  with  gray  matter,  a 
section  of  which  is  lenticular  in  shape ;  and  a  posterior  por- 
tion, plano-concave  in  shape,  and  composed  of  two  layers, 
which  is  the  continuation  of  the  spinal  cord  and  medulla 
oblongata,  except  the  anterior  pyramids  in  front,  and  the 
restiform  bodies  behind.  These  two  portions  of  the  pons 
Varolii  are  easily  separated  from  each  other  by  dividing  the 
anterior  pyramid  and  gently  tearing  the  transverse  fibres  of 
the  pons  from  those  behind  which  have  a  longitudinal  direc- 
tion. These  portions  of  the  pons  are  distinct  in  function, 
that  in  front  being  commissural  containing  the  great  com- 
missure of  the  cerebellum  and  the  motor  tract,  and  that 
behind  belonging  to  the  sensory  tract  and  the  column  of  gray 
matter  called  the  fascicula  teretes,  which  is  a  continuation  of 
the  gray  column  of  the  spinal  cord. 

These  parts  may  be  more  readily  understood  by  a  dissec- 
tion from  before  backwards.  The  anterior  division  of  the  pons 
is  composed  of  two  layers,  and  the  posterior  division  also  of 
two  layers,  which  will  be  described  in  succession.  The  super- 
ficial layer  of  the  anterior  division  of  the  pons  has  before 
been  described  as  consisting  of  three  parts,  an  inferior  portion 
which  has  a  transverse  direction,  a  middle  portion  which  is 
transverse  on  each  side  of  the  basilar  groove  and  laterally 
arches  downward  to  overlap  the  extremities  of  the  inferior 
fibres,  and  an  upper  portion  which  emerges  from  the  posterior 
perforated  space  and  passing  outwards  and  backwards  around 


THE    PONS    VAROLII. 


45 


the  crura  cerebri  to  terminate  in  the  cerebellum  along  with  the 
restiform  bodies.  The  superficial  layer  of  the  pons  Varolii 
is  the  great  transverse  commissure  of  the  cerebellum,  excej^t- 
ing  its  superior  fibres,  which  are  the  restiform  fibres  from 
the  floor  of  the  fourth  ventricle,  as  before  stated.  If  this 
layer  of  fibi'es,  which  is  the  commissural  layer,  be  divided  in 
an  anterio-posterior  direction,  it  will  be  seen  to  average  one 
sixth  of  an  inch  in  thickness.  Beneath  this  layer  is  a  netwoi'k 
of  transverse  and  longitudinal  fibres  interspersed  with  gray 
matter,  and  is  called  the  formatio  reticularis  of  the  pons 
Varolii.  The  network  is  composed  of  the  deep  transverse 
fibres  of  the  middle  peduncle  of  the  cerebellum,  interlacing 
with  fibres  which  descend  from  the  crustae  of  the  crura  cerebri. 
The  fibres  of  a  crusta  are  disposed  in  laminae,  similar  to 
those  of  the  internal  capsule,  and  are  placed  one  behind 
the  other  in  the  crus,  but  as  they  descend  into  the  pons  they 
are  separated  from  each  other  in  order  that  the  transverse 
fibres  of  the  deep  layer  of  the  pons,  also  disposed  in  laminae, 
may  be  inserted  between  those  of  the  crusta  as  they  descend. 
The  vesicular  matter  of  the  pons  is  interspersed  throughout 
this  formatio  reticularis,  but  is  more  concentrated  in  the  middle 
of  the  posterior  portion  of  this  part  of  the  pons.  The  gray 
matter  of  the  pons  is  called  its  nucleus,  and  is  continuous 
above  with  the  locus  niger  or  vesicular  tract  of  the  crus 
cerebri. 

The  fibres  derived  from  the  anterior  pyramids  of  the 
medulla  oblongata  pass  upward  with  the  longitudinal  fibres 
of  the  pons  to  the  crusta  and  internal  capsule.  The  reticulated 
layer  is  the  motor  portion  of  the  pons  Varolii.  It  consists  of 
the  crusta,  the  fibres  of  the  anterior  pyramid,  the  deep  layer 
of  the  transverse  fibres  of  the  middle  peduncle,  together  with 
the  gray  matter,  or  the  ganglion  of  the  pons  Varolii.     The 


Superficial  layer 
of    tlie    anterior 
portion   of    the 
pons  is  the  great 
commissure  of 
cerebellum.  Figs 
9-34-35. 


Deep   layer  of    tin 


5  of  the 
Figs.  34-35. 


10  to  13-33-33. 
30*-21i'(SN). 


46  ARCHITECTURE    OF    THE    BRAIN. 


The  ganglion  the  of 
pons  i^  the  exter- 
nal   1  asal  gangli- 


Longitudinal  fib 
of  the  Vai-oli 
Figs.  11  to  14. 


ganglion  of  the  pons  is  the  motor  basal  ganglion  of  the  cere- 
bellum, and  is  the  analogue  of  the  lenticular  ganglion  of  the 
cerebrum. 

The  posterior  division  of  the  pons  Varolii,  or  that  portion 
of  it  which  is  a  continuation  of  the  spinal  cord,  can  be  better 
studied  by  the  removal  of  the  part  which  has  just  been 
described.  If  the  anterior  pyramids  and  the  lateral  attach- 
ments of  the  pons  to  the  cerebellum  are  divided,  and  the  anter- 
ior portion  of  the  pons  is  gently  lifted  from  its  bed,  it  will  sep- 
arate from  a  broad  band  of  longitudinal  fibres,  extending  from 
the  medulla  oblongata  to  the  crura  cerebri.  By  a  division  of  the 
crusta  above,  the  whole  can  be  removed  in  a  mass,  leaving  a 
broad  excavation  flat  from  side  to  side  and  concave  from  above 
downwards.  This  surface  is  divided  into  lateral  halves  by  an 
elevated  ridge  of  torn  fibres  which  extends  longitudinally 
from  the  anterior  median  fissure  of  the  medulla  oblongata  to 
the  center  of  the  interpeduncular  space  above.  The  central 
ridge  is  composed  of  the  ruptured  fibres  of  the  raphe.  The  sur- 
face exposed  presents  the  appearance  of  a  broad  transverse 
groove,  and  lodges  the  anterior  portion  of  the  pons  Varolii. 
Upon  each  side  of  the  anterior  median  fissure,  along  the  lower 
pyramids,  boi'dcr  of  the  groove,  are  the  divided  ends  of  the  anterior 
Figs. 9-  pyiamids  which  project  upwards  as  the  extremities  of 
rounded  cords.  Upon  the  outer  s'de  of  these  are  the  upper 
extremities  of  the  olivary  l^odies,  external  to  which  are  the 
lateral  tracts  of  the  medulla  oblongata,  and  more  externally 
the  arched  fibres  of  the  restiform  bodies.  Emerging  from 
beneath  the  divided  extremities  of  the  anterior  pyramids,  and 
from  between  the  olivary  bodies  and  the  raphe,  are  two  tracts, 
one  on  either  side,  which  ascend  in  an  outward  direction, 
obliquely  to  the  upper  and  outer  margins  of  this  surface  where 
they  become  superficial.      They  overlap  the  anterior  part  of 


ilevated   ri 

idge  di 

viding    th 

e    le.n- 

niscus     CI 

-     fillet 

longitndin 

ally    in 

the  middli 

5  line. 

See  raphe 

.     Figs, 

11  to  14. 

nedull 


Fig.  12, 


Anterior  root  zc 
or  lateral  trac 
llie  medulla. 
Figs.  7-10-1 1-12 


fourth    ventric 
Figs.  11-12-13. 


THE    PONS    VAROLII.  47 

the  processes  and  terminate  in  the  testes  and  brachia  pos- 
terius.  These  tracts  are  the  continuation  of  the  fundamental 
root  zones  of  the  spinal  cord.  They  have  been  called  the 
anterior  layer  of  the  lemniscus,  or  fillet,  but  are  distinct  tracts 
of  fibres  which  connect  the  corpora  quadragemina  with  the 
anterior  horns  of  the  gray  matter  of  the  spinal  cord,  and 
do  not  belong  to  the  same  system  of  fibres  as  the  fillet. 
Beneath  the  layer  just  described,  is  a  longitudinal  layer  of  oiivary  tasc 
fibres  derived  from  the  olivary  bodies  of  the  medulla  oblon- 
gata, and  is  called  the  olivary  fasciculus.  Under  the  olivary 
fasciculus  is  a  similar  layer  which  is  continuous  below  with  the 
lateral  columns  of  the  medulla  oblongata,  and  the  anterior  root 
zones  of  the  spinal  cord.  Behind  this  layer  is  one  which  is 
derived  from  the  gray  matter  of  the  fasciculi  teretes  and  which 
joins  the  fillet  above  and  from  the  inner  side  of  the  restiform 
body.  The  three  layers  last  described  constitute  the  fillet 
proper,  but  it  will  be  convenient  in  ordinary  to  say,  that  these 
four  layers  unite  in  forming  the  longitudinal  layer  of  this 
portion  of  the  pons  Varolii.  The  outer  margin  of  the  fillet 
forms  the  internal  boundary  of  a  triangle,  which  is  bounded 
above  by  the  processus,  and  behind  by  the  restiform  body, 
and  is  called  the  restiform  triangle.  ^Fi'»l°9"to'iT"^'^ 

The  vesicular  layer  of  the  posterior  portion  of  the  pons 
Varolii  underlies  the  floor  of  the  fourth  ventricle,  and  Ijeiog 
elevated  upon  its  posterior  surface  is  called  the  fasciculi 
teretes.  This  layer  is  continuous  below  with  the  gray  col- 
umns of  the  spinal  cord,  which,  in  the  floor  of  the  fourth 
ventricle,  are  separated  behind,  so  that  the  posterior  cornua 
are  external  upon  the  sides,  and  the  anterior  cornua  lie 
together  along  the  median  fissure  of  the  ventricle.  On  ac- 
count of  this  disposition  of  the  anterior  and  posterior  cornua, 
the  centres  of  the  motor  nerves  of  the  medulla  oblongata  are 


Fasciculi  tere 
Figs.  1015. 


rhe  fourth  ventri- 
cle. Figs.  8-10- 
15-26. 


48  ARCHITECTURE    OF   THE    BRAIN. 

placed  along  the  median  line  of  the  ventricle,  and  those  of 
the  sensory  nerves  upon  its  sides. 

The  fourth  ventricle: — The  fourth  ventricle  is  situated 
behind  the  pons  Varolii  and  the  upper  half  of  the  medulla 
oblongata.  It  is  bounded  below,  on  each  side,  by  the  rest- 
iform  bodies,  and  above  by  the  inferior  margins  of  the  pro- 
Root.  Figs. 8-26.  cesses.  Its  roof  is  formed  by  the  processes  on  each  side,  and 
by  the  valve  of  Vieussens  in  the  middle.  It  is  about  one  inch 
and  a  half  in  length  from  above  downwards,  and  about  three- 
quarters  of  an  inch  in  width  at  its  wadest  part,  which  is  be- 
tween the  upper  j)ortion  of  the  restiform  bodies,  its  depth  from 
above  downwards,  from  the  valve  of  Vieussens  to  the  median 
fissure,  is  about  five-eighths  of  an  inch.  Its  floor  is  lozenge 
shaped  and  pointed  at  either  extremity,  its  upper  extremity  is 
continued  by  the  iter  to  communicate  with  the  third  ventricle. 
Its  lower  extremity  is  continuous  with  the  central  canal  and 
the  posterior  median  fissure  of  the  spinal  cord.  The  median 
fissure  of  the  fourth   ventricle  divides  its  floor  into  lateral 

"^ -^-  halves,  and  is  the  posterior  boundary  of  the  raphe.  The  resti- 

form bodies  are  elevated  on  each  side  above  the  level  of  the 
floor  of  the  ventricle,  and  their  gradual  approach  and  junction 
at  the  lower  extremity  of  the  ventricle  resembles  a  pen  in 
appearance,  hence  the  lower  extremity  of  the  ventricle  is 
1ut!"''Figs.Tia       called  the  calamus  scriptorius. 

Below  are  two  slight  elevations  or  grey  tubercles,    one 
upon   each  side  of   the    apex   of   the  ventricle,   the  clavate 

F^^Ts-'ir''"'  nucleii,  which  are  the  terminations  of  the  posterior  pyra- 
mids of  the  medulla  oblongata.  Directed  upwards  and 
outwards  from  these  tubercles,  along  the  floor  of  the  fourth 
ventricle  internal  to  the  restiform  body  on  either  side,  is  a 

)rigjn  of  tlie  deep  ''  ' 

layer  of  the  fillet     ti'act  of  whitc  fibrcs  wWch  passes  through  the  restiform  trian- 

in  the  fourth  ven-  ■*■  ° 

tricie.  Figs. 8-10     g]g^  ^q  jq^q  the  fillct.      Thls  ti'act  forms  the  posterior  Layer  of 


tricle.  Figs.  8-10- 


THE    PONS    VAROLII. 


49 


the  fillet,  and  a  portion  of  it  turns  outward  with  the  restiform 
body  to  the  cerebellum.  It  also  receives  the  anterior  root  of 
the  eighth  nerve  as  this  root  turns  downward  from  the  resti- 
form triangle  into  the  fourth  ventricle  to  reach  the  auditory 
nucleus,  which  is  situated  beneath  the  floor  of  the  ventricle  at 
the  side  of  calamus  scriptorius. 

At  the  lower  part  of  the  restiform  body,  external  to  the 
ventricle,  and  above  the  clavate  nucleii,  is  a  broad  elevation 
covered  by  white  fibres  which  marks  the  situation  of  the 
restiform  nucleus.  The  restiform  nucleus  is  the  superior  ter- 
mination of  the  posterior  column  of  the  medulla  oblongata 
and  spinal  cord,  and  it  is  the  origin  of  a  large  portion  of  the 
fibres  which  constitute  the  restiform  body. 

The  floor  of  the  fourth  ventricle  is  gray  in  color,  some 
parts  of  it  presenting  bluish  elevations  which  are  the  centres 
of  nerves,  and  are  called  loci  cerulii.  If  the  sides  of  its  me- 
dian fissure  are  separated,  the  torn  surfaces  present  a  striated 
appearance  of  antero-posterior  oblique  fibres,  which  inter- 
mingle across  the  median  line.  The  fibres  thus  separated 
compose  the  raphe  before  described. 

Crossing  the  surface  of  the  floor  of  the  fourth  ventricle, 
about  its  middle,  are  several  stride,  which  are  the  striae  trans- 
transvers?e.  The  inferior  stride  are  derived  externally  from 
the  posterior  root  of  the  eighth  nerve  (auditory),  which  pass 
inward  beneath  and  across  the  flexion  of  the  restiform  body  to 
the  floor  of  the  fourth  ventricle,  to  enter  the  raphe,  in  the  me- 
dian line,  among  the  fibres  of  which  they  are  lost.  The  superior 
striae  transversie  commence  above  the  arch  of  the  restiform 
bodies  upon  the  outer  margin  of  the  floor  of  the  ventricle, 
and  are  directed  downward  and  inward,  obliquely  from  the 
restiform  triangle  to  the  raphe. 


eiKl.th  ner 
Figs.  8-9. 


Restifor: 
Figs.  8 


jtnas  transversae. 
Figs.  8-10. 


Posterior  root  of 
auditory  nerve. 
Figs.  8-10. 


Root  of    tlie   facial 


50 


ARCHITECTURE    OF    THE   BRAIN. 


lavity  of  the  fourth 
ventricle.  Figs. 
8-10-26-25*  to  29*. 


They  may  be  traced  as  far  forward,  and  below,  as 
the  inferior  margin  of  the  pons  Varolii,  at  the  anterior  me- 
dian fissure  of  the  medulla.  These  fibres  are  continuous  out- 
wardly on  the  same  side  with  the  seventh  nerve  (facial),  and, 
internally,  at  the  anterior  median  fissure,  with  the  anterior 
pyramid  of  the  opposite  side. 

The  roof  of  the  fourth  ventricle  is  arched  from  side  to  side, 
and  diminishing  in  size  gradually  towards  its  anterior  extrem- 
ity encloses  a  conical  shaped  cavitiy  which  is  contracted 
above  to  be  continuous  with  the  iter.  This  cavity  lodges 
the  inferior  vermiform  process  of  the  middle  lobe  of  the 
cerebellum,  the  superior  vermiform  process  resting  upon  the 
upper  surface  of  the  parts  forming  the  roof  of  the  fourth 
ventricle. 

The  parts  which  form  the  roof  the  fourth  ventricle,  viz. : 
the  processes  and  the  valve  of  Vieussens,  which  enter  the 
upper  part  of  the  hilus  of  the  cerebellum  are  connected  behind 
with  the  dentate  body.  In  front  they  assist  in  the  formation 
of  the  peduncles  of  the  cerebrum. 

To  recapitulate:  The  pons  Varolii  is  divided  into  two  por- 
tions, an  anterior  or  cerebellar,  and  a  posterior  or  spinal. 
These  portions  include  from  before  backwards:  first,  a  trans- 
verse layer  which  is  the  commissure  of  the  cerebellum;  second, 
a  reticulated  and  vesicular  layer,  which  is  the  motor  tract ; 
third,  a  longitudinal  layer,  the  lemniscus  or  fillet;  fourth,  a 
vescicular  layer  or  the  fasciculi  teretes ;  and  fifth,  the  resti- 
form  bodies  or  inferior  peduncles  of  the  cerebellum,  which 
will  be  described  with  the  medulla  oblongata  in  connection 
with  the  tracts  from  which  they  are  derived.  The  relation  of 
these  layers  to  each  other  should  be  recollected, in  order  to  tra,ce 
their  distribution  above  in  the  formation  of  the  crus  cerebri 
and  internal  capsule,  as  well  as  their  connections  below  with 
the  medulla  oblongata  and  spinal  cord. 


THE  MEDULLA  OBLONGATA  AND  SPINAL  CORD. 


These  parts  of  the  cerebro  spinal  axis  are  so  intimately 
associated  in  general  structure,  and  in  the  contitiuity  of  the  Medunaands  inai 
tracts  of  grey  and  white  columns  of  which  they  are  consti-  cord.  Figs. -to in. 
tuted,  that  it  will  be  convenient  to  describe  them  together. 
The  medulla  oblongata  is  properly  the  upper  portion  of  the 
spinal  cord,  in  which  there  is  a  rearrangement  of  its  columns 
and  tlie  addition  of  important  nerve  centers.  The  spinal  cord 
possesses  the  distinction,  that  in  its  structure  the  vesicular  or 
grey  matter  is  enclosed  within  the  white  matter,  while  in  that 
of  the  brain  the  gray  matter  is  external. 

The  cord  including  the  medulla  is  about  eighteen  inches 
in  length,  extending  from  the  lower  border  of  the  pons 
Varolii  downward  in  the  spinal  canal  to  about  the  level  of  the 
lower  border  of  the  first  lumbar  vertebra.  It  terminates  in 
a  slender  filament,  the  filum  terminale,  which  contains  a  small 
amount  of  gray  matter  and  ends  at  the  sacral  canal. 

The  spinal  cord  is  rounded  in  transverse  section,  is  divided     xransve 

Figs,  t 

into  lateral  halves  by  an  anterior  and  posterior  median  fissure, 
the  former  extending  upward  to  the  lower  border  of  the  pons 
Varolii,  and  the  latter  to  the  separation  of  the  posterior  col- 
umns of  the  cord  which  form  the  sides  of  the  fourth  ventri- 
cle. About  an  inch  and  a  half  below  the  inferior  border  of 
the  pons  the  anterior  median  fissure  is  partially  obstructed  by 
a  tract  of  decussating  fibres,  which  are  those  of  the  anterior 
pyramids  of  the  medulla  oblongata.  The  lower  extremity 
of  the  decussation  of   the  pyramids  is  the  line  of    division       Ta""^' 


Ves: 


52  ARCHITECTURE    OF   THE    BRAIN. 

between  the  spinal  cord  proper  wliich  is  the  lower  portion, 
and  the  medulla  oblongata  above.  At  the  point  of  decussa- 
tion there  is  an  interruption  in  the  grey  elements  of  the  spinal 
cord,  produced  by  tracts  of  white  fibres,  which  are  directed 
forward  from  the  deep  fibres  of  the  lateral  columns  of 
the  cord,  to  become  superficial  in  front  of  the  medulla 
oblongata.  The  lateral  halves  of  the  cord  are  united  in  the 
middle  by  a  commissure,  which  is  white  in  front  and  grey 
behind.  In  the  middle  of  the  grey  commissure  is  a  minute 
canal,  the  ventricle  of  the  spinal  cord,  which  extends  through 
its  length  and  opens  into  the  fourth  ventricle  at  the 
apex  of  the  calamus  scriptorius.  The  fourth  ventricle  is 
a  conthauation  of  the  centrtd  canal  of  the  spinal  cord,  and  is 
formed  by  a  defect  of  the  posterior  commissure  of  the  cord 
and  a  separation  of  its  posterior  colunms  into  the  resti- 
form  bodies.  The  fourth  ventricle  begins  in  the  middle  of 
the  posterior  surface  of  the  medulla  oblongata. 

The  grey  substance  of  the  spinal  cord  is  arranged  in  two 
columns,  one  on  each  side,  united  by  a  grey  commissure 
which  contains  the  central  canal.  The  anterior  portion 
nT  of  each  column  is  called  its  anterior  horn  and  is  the  motor 
vesicular  column  of  the  cord ;  the  posterior  projection  or 
column  of  grey  matter  is  called  the  posterior  grey  horn, 
or  sensory  arm.  At  the  junction  of  the  posterior  cornu 
with  the  grey  commissure  is  a  slender  vesicular  column, 
of  Clarke.  Fig.  callcd  the  vesicular  column  of  Clarke.  This  column  is  prob- 
ably the  cerebellar  element  of  the  spiaal  cord,  since  it  is 
connected  directly  with  the  cerebellum  by  the  direct  cere- 
bellar tract,  and  degenerates  along  with  it  in  the  disease 
known  as  cerebello  spinal  ataxia. 

The  anterior  vesicular  columns  of  the  spinal  cord  are  dis- 
turbed or  interrupted  by  the  decussation  of  the  anterior  pyra- 


Fig. 


THK    MEDULLA    OBLONGATA    AND    SPINAL    CORD.  53 

mids  of  the  medulla  about  au  inch  and  a  half  below  the 
pons  Varolii.  As  the  vesicular  columns  of  the  cord  apj^roach 
the  fourth  ventricle  the  posterior  cornua,  or  posterior  vesicu- 
lar columns,  gradually  diverge,  and  the  anterior  cornua  ap- 
proach each  other  toward  the  median  line.  In  the  floor  of 
the  fourth  ventricle  the  grey  columns  are  spread  into  a  grey 
sheet,  which  forms  the  fasciculi  teretes  of  the  floor  of  the 
ventricle;  the  anterior  columns  lying  along  the  median  fissure, 
and  the  posterior  along  the  sides  of  the  floor  of  the  ventricle. 
The  sensory  roots  of  the  spinal  nerves  terminate  in  the 
posterior  vesicular  columns  of  the  spinal  cord,  and  the  sen- 
sory cranial  nerves  in  masses  of  vesicular  matter  in  the  outer 
part  of  the  floor  of  the   fourth  ventricle.      The  motor  roots 

Connections  c 

of  the  spinal  nerves  are  connected  with  the  anterior  vesiclar       spinainervei 

the  grey  hoi-: 

columns  of  the  cord,  and  the  motor  cranial  nerves  with  the  F's-  sb. 
motor  centers  along  the  middle  of  the  floor  of  the  ventricle. 
The  roots  of  the  spinal  nerves  emerge  from  the  sides  of 
the  spinal  cord;  the  anterior  roots  in  a  line  about  one-third  of 
the  distance  laterally  on  each  side  of  the  anterior  median 
fissure,  and  the  posterior  roots  also  about  one-third  of  the 
distance  outward  upon  each  side  of  the  posterior  median  fis- 
sure, dividing  the  spinal  cord  on  each  side  into  three  columns, 
anterior,  lateral  and  posterior.  Each  column  of  the  cord 
is   subdivided   into    tracts    which    can    be    traced    through       '=°'";!™ 

o  cord. 

the  medulla  to  join  with  the  several  divisions  of  the  pons 
Varolii  described,  and  with  the  restiform  bodies  or  inferior 
peduncles  of  the  cerebellum. 

The  spinal  cord  is  variable  in  size  in  diff'erent  localities, 
due  to  the  dift'erence  in  the  volume   of    the  spinal  nerves     oescripti 
received  by  it  at  certain  points.     The  lumbar  enlargement  is 
near  the  lower  end  of  the  cord  and  receives  the  nerves  from 
the    lower   extremities.     The   cervical   enlargement   extends 


Anterior,    lateral 
and   posterior 


t   tlif 
1  cord. 


64  ARCHITECTURE    OF    THE    BRAEST. 

from  the  third  cervical  to  the  first  dorsal  vertebra,  receives 
the  nerves  from  the  upper  extremity  and  is  somewhat  larger 
than  that  of  the  lumbar  region.  The  medulla  oblongata  is 
the  uppermost  enlargement  of  the  spinal  cord,  it  lies  within  the 
cranial  cavity  and  is  sometimes  called  the  bulb.  This  part  of 
the  spinal  cord  contains  the  centers  which  control  the  func- 
tions of  respiration  and  circulation,  and  is  therefore  one  limb 
of  the  tripod  which  immediately  sustains  life.  It  also  co- 
ordinates the  muscles  that  perform  the  acts  of  deglutition 
and  speech,  besides  other  important  functions.  Symptoms 
indicating  defection  of  this  part  of  the  central  nervous  sys- 
tem are  of  grave  import,  and  are  spoken  of  as  bulbar  symp- 
toms, bulbar  paralysis,  etc.  Certain  diseases  originate  from 
functional  or  organic  disturbance  of  the  medulla,  therefore  a 
familiarity  with  its  anatomy  is  fundamental  to  the  diagnosis 
of  these  diseases,  and  also  assists  in  the  eaidy  recognition  of 
those  symptoms  which  denote  the  approach  of  death.  The  rela- 
tions of  its  tracts  to  the  several  nerves  of  distinct  function 
provide  ceitain  combinations  of  symptoms  by  which  the  anato- 
mist can  determine  the  exact  situation  and  extent  of  a  lesion. 

In  order  that  the  relations  and  the  continuity  of  the  col- 
umns and  tracts  of  the  spinal  cord  with  those  of  the  medulla 
oblongata,  and  the  tracts  of  the  latter  with  the  divisions  of 
the  pons  Varolii  and  with  the  cerebellum,  may  be  more 
clearly  understood,  we  will  locate  and  name,  first,  the  tracts 
of  the  spinal  cord,  then  those  of  the  medulla,  and  afterward 
associate  them  with  each  other,  and  with  the  divisions  of  the 
pons  which  have  before  been  described. 

The  spinal  cord  proper,  as  stated,  is  that  which  extends 
below  the  decussation  of  the  anterior  pyramids  of  the  me- 
dulla oblongata.  It  is  uniform  in  structure,  size  and  appear- 
ance except   the    enlargements    of   its   cervical   and    lumbar 


15-38. 


THE    MEDULLA    OBLONGATA    AND    SPINAL    CORD.  55 

regions,  and  that  its  fascicular  tracts,  or  the  white  substance 
diminishes  in  quantity  from  above  downward. 

The  grey  columns  and  the  central  canal,  or  ventricle  of 
the  cord,  have  been  described ;  the  former  as  being  continu- 
ous with  the  grey  matter  in  the  floor  of  the  fourth  ventricle, 
and  the  latter  as  a  part  of  the  ventricular  system  which 
extends  through  the  whole  length  of  the  cerebro  spinal  axis. 

It  remains  to  trace  the  tracts  which  form  the  white  col-     ^        ,  ,      .    , 

Tracts  or  the  spinal 

umns  of  the  cord  and  to  describe  their  relations.  '^T.t  ^"^^' 

The  relation  of  these  tracts  will  be  more  easily  under- 
stood by  an  examination  of  a  transverse  section  of  the  spinal 
cord  as  represented  in  figure  38,  which  exhibits  the  division 
of  the  cord  into  three  columns  by  the  anterior  and  posterior 
roots  of  the  spinal  nerves. 

Each  of  the  three  columns  of  the  cord  are  divided  into 
tracts,  the  anterior  and  the  posterior  each,  into  two,  and 
the  lateral  into  four.  Each  of  these  tracts  are  endowed 
with  a  specific  function,  and  are  arranged  in  bundles  which 
can  be  se2:)arated  in  part  by  careful  dissection,  traced  by 
the  degeneration  observed  as  the  result  of  disease,  and  also 
by  the  observation  of  the  development  of  the  embryo. 

Upon  either  side  of  the  anterior  median  fissure  is  a  small 
column  which  descends  directly  from  theanterior  pyramid  of     dsi 
the  medulla,  called  the  direct  pyramidal  tract,  or  column  of       i 
Tiirck.     The  remaining  portion  of   the  anterior  column  of 
the  cord,  which  is  much  the  larger  part,  is  called  the  funda- 
mental root  zone,  because  it  is  among  the  first  elements  to  de-       " 
velope  in  the  spinal  cord. 

Oq  either  side  of  the  posterior  median  fissure  is  another 
small  column,   called    the  posterior  median  column,  or  col- 
umn of  Gall,  which  is  supposed  to  be  the  respiratory  tract  of      °> 
the  cord.   The  remaining  portion  of  the  posterior  column  of  the 


56 


ARCHITECTT'EE    OF    THE    BRAIN. 


Posterior  root  zone 
or  column  of  Bur 
dach. 


Crossed  pyr 
tract. 


Crosses  the  media 
line  to  join  th 
anterior  pyrami 
of  the  opposil 
side.     Fig.  14. 


cord,  which  is  much  Lirger  than  the  preceding,  is  called  the 
posterior  root  zone,  the  cuneate  fasciculus,  or  the  column  ( f 
Burdach.  It  is  the  sensory  column  of  the  spinal  cord,  dis- 
ease of  which  disorders  muscular  coordination,  as  in  the 
case  of  progressive  locomotor  ataxia. 

The  lateral  column  of  the  spinal  cord  is  constituted  of 
four  fasciculi  or  tracts,  and  is  included  between  the  lines  of 
emergence  of  the  anterior  and  posterior  roots  of  the  spinal 
nerves.  These  tracts  are:  first — a  ribbon  like  tract  situated 
directly  in  front  of  the  extremity  of  the  posterior  horn  of 
grey  matter  of  either  side,  and  occupying  the  surface  of  the 
lateral  column  for  about  half  its  extent.  This  tract  is  con- 
nected in  the  spinal  cord  with  the  grey  column  of  Clarke,  and 
is  continued  above  upon  the  lateral  surface  of  the  medulla 
and  restiform  body  to  the  cerebellum.  It  suffers  degenera- 
tion in  the  disease  known  as  cerebello  spinal  ataxia,  which 
runs  a  rapid  course,  affecting  principally  the  nutritive  func- 
tions of  the  body.  Second — beneath  the  direct  cerebellar 
ti'act,  and  anterior  to  the  posterior  horn  of  the  grey  matter,  is 
a  rounded  fasciculus  called  the  crossed  pyramidal  tract.  This 
tract  is  connected  with  the  vesicular  matter  of  the  posterior 
horn  of  the  cord,  and  above  with  the  anterior  pyramid  of  the 
opposite  side  of  the  medulla  oblongata.  It  decussates  with 
the  crossed  pyramidal  tract  of  the  opposite  half  of  the  spinal 
cord  in  the  anterior  median  fissure,  at  the  lower  extremity  of 
the  medulla.  Beyond  the  decussation  it  unites  with  the 
opposite  direct  pyramidal  tract  to  form  the  anterior  pyramid 
of  the  opposite  side  of  the  medulla.  The  crossed  pyramidal 
tract  is  the  motor  column  of  the  cord,  and  possibly  the  offioe 
of  the  direct  pyramidal  tract  is  to  co-ordinate  the  muscles  of 
one  side  of  tlie  body  with  those  of  the  other.  Third  — 
between  the  columns  just  described,  and  the  anterior  cornu 


THE    MEDULLA    015L0NGATA    AND    SPINAL    CORD. 


57 


of  grey  matter  and  the  anterior  roots  of  the  spinal  nerves, 
is  a  large  column  of  fibres  forming  the  anterior  portion 
of  the  lateral  column  of  the  cord.  It  is  called  the  anterior 
root  zone,  and  in  the  spinal  cord  is  supposed  to  contain 
longitudinal  fibres  that  connect  the  segments  of  the  cord 
together,  and  also  a  sensory  tract  (Gowers)  which  is  continued 
into  the  cerebrum.  This  tract  is  nearly  uniform  through- 
out the  spinal  cord,  and  is  continued  upon  the  side  of 
the  medulla  to  join  the  fillet.  Fourth — internal  to  the 
three  tracts  just  described  and  lying  next  to  the  concave 
outer  surface  of  the  grey  column  of  the  cord,  is  a  reticulated 
column  composed  of  the  interlacing  fibres  of  the  other  fas- 
ciculi of  the  lateral  column  of  the  spinal  cord.  This  tract  is 
the  formatio  reticularis  of  the  cord,  and  corresponds  to  the 
corona  radiata  of  the  cerebrum  and  cerebellum.  It  is  also 
called  the  mixed  lateral  column,  and  is  not  properly  a  distinct 
fasciculus  of  the  spinal  cord. 

The  MEDULLA  OBLONGATA. — The  lower  portion  of  tlie  me- 
dulla corresponds  to  the  spinal  cord  in  size,  shape,  and  in  the 
arrangement  of  its  columns,  with  the  exception,  that  the 
crossed  pyramidal  tracts  of  the  lateral  columns  of  the  cord, 
pass  forward,  decussate  with  each  other,  and  join  the 
direct  pyi'amidal  tracts  of  the  anterior  columns,  to  form  the 
anterior  pyramids  of  the  medulla.  The  posterior  median 
columns  of  the  cord  are  called,  in  this  situation,  the  posterior 
pyramids  of  the  medulla,  and  terminate  above  in  the  clavate 
nucleii  at  the  apex  of  the  fourth  ventricle.  The  posterior 
column  of  the  cord  (Burdach's)  occupies  the  same  relative 
position  in  the  medulla  as  in  the  spinal  cord,  and  terminates 
above  in  the  restiform  nucleus,  which  is  situated  in  the  resti- 
form  body  above  and  external  to  the  clavate  nucleus.  The 
direct  cerebellar  tract  is  continued  upward,  on  the  surface  of 


Posterior  pyran 
Figs.  8-10-15. 


stitorin 
s.     Figs. 


58 


AECHITECTUEE    OF    THE    BRAIN. 


Anterior  i 
or  latera 
medulla 
10  to  I-l. 


Fundamental  root 
zone.  Figs.  9-11 
to  U-36. 


Relation  of  the 
tracts  which  from 
the  lower  part  of 
the  medulla. 
Figs.  7-9  10-36. 


Upper  portion  t 
the  medulla. 
Figs.  9-10-36. 


Section 
of    the 
Fig.  36. 


nd  raphe 
medulla. 


the  medulla  and  the  restiform  body,  to  the  cerebellum.  This 
tract  covers  the  restiform  nucleus  so  that  the  latter  is  not 
exposed  upon  the  surface.  The  anterior  root  zone,  or  lateral 
tract  of  the  medulla,  passes  upward  upon  the  side  of  the  me- 
dulla to  the  lower  extremity  of  the  olive  where  it  becomes 
compressed,  between  the  latter  and  the  restiform  body,  into  a 
narrow  tract  which  above  forms  the  middle  layer  of  the  fillet 
of  the  pons.  The  fundamental  root  zone  above  the  cord  is 
crowded  outward  by  the  anterior  pyramid,  as  far  as  the  lower 
extremity  of  the  olive.  Just  below  this  point,  it  is  flattened 
in  front  to  accommodate  the  decussation  of  the  pyramids  and 
disappears  from  the  surface  of  the  medulla  to  get  behind  the 
pyramid  between  the  olive  and  the  raphe,  in  which  situa- 
tion this  tract  is  prismatic  in  shape,  its  sides  being  in  relation 
to  the  parts  just  mentioned.  Above  the  olive,  it  escapes  to 
form  a  flat  layer  of  fibres  upon  the  fillet,  and  terminates  above 
in  the  testes  and  brachium  posterius. 

The  tracts  on  either  side  of  the  medulla  oblongata  which 
form  its  lower  part  from  before  backward  are:  the  anterior 
pyramid,  the  fundamental  root  zone,  the  anterior  root  zone  or 
lateral  tract,  the  direct  cerebellar  tract,  the  posterior  column, 
and  the  posterior  pyramid. 

The  upper  part  of  the  medulla  is  attached  to  the  pons 
Varolii,  and  is  connected  with  the  cerebellum  by  the  restiform 
bodies,  or  inferior  peduncles  of  the  cerebellum.  The  medulla 
gradually  enlarges  as  it  ascends  from  the  cord;  its  upper 
extremity  is  about  three-quarters  of  an  inch  from  side 
to  side,  and  about  flve-eighths  of  an  inch  from  before  back- 
ward. The  lower  portion  of  the  fourth  ventricle  is  behind 
the  upper  half  of  the  medulla  oblongata,  and  the  raphe  ex- 
teuding  from  the  median  fissure  of  the  ventricle  forward  to 
the  anterior  median  fissure  of    the   medulla,  divides  it  into 


THE    MEDULLA    OBLONGATA    AND    SPINAL    CORD. 


59 


lateral  halves.  A  transverse  section  of  the  medulla,  seen  in 
figure  36,  or  better  in  a  section  one-eighth  of  an  inch  above  it, 
is  somewhat  triangular  in  shape,  with  truncated  angles,  and 
shows  the  relation  of  the  tracts  which  are  continued  upwards 
from  its  lower  portion.  The  relations  of  these  tracts  are  on 
either  side,  beginning  from  the  anterior  median  fissure  and 
raphe  in  front:  the  anterior  pyramid;  the  olivary  body,  or 
olive;  a  triangular  tract  between  the  olive  and  raphe,  beneath 
the  pyramid,  called  the  fundamental  root  zone;  the  lateral 
tract,  or  anterior  root  zone,  compressed  between  the  olive  and 
restiform  body;  and  the  restiform  body  or  inferior  peduncle 
of  the  cerebellum  within  which  is  seen  the  restiform  nucleus. 
Figure  36. 

The  parts  of  the  medulla  which  have  not  been  described 
are  the  anterior  pyramids,  the  olive,  and  the  restiform  body. 
The  arciform  fibres  and  the  fibres  from  the  raphe  will  be 
described  incidentally  with  the  others  above  mentioned. 

The  anterior  pyramids  of  the  medulla  emerge  from  the 
middle  of  the  lower  border  of  the  pons  Varolii  as  two 
rounded  cords,  one  on  each  side  of  the  anterior  median  fissure 
and  raphe  of  the  medulla  oblongata.  They  descend  s'de  by 
side,  separated  by  the  anterior  median  fissure,  to  the  point  of 
decussation  at  the  lower  extremity  of  the  medulla  where  each 
divides  into  two  portions:  first,  a  small  tract  which  continues 
on  the  same  side  of  the  anterior  median  fissure  of  the  spinal 
cord,  and  is  the  anterior  median  column,  or  column  of  Tiirck; 
and,  a  large  tract  which  breaks  up  into  several  bundles  of 
fibres  that  pass  backward  and  outward,  interrupting  the  an- 
terior horns  of  the  grey  columns  of  the  cord,  and  reaching 
the  anterior  surface  of  the  posterior  horns,  forms  the  crossed 
pyramidal  tract  of  the  opposite  side  of  the  spinal  cord. 


eduUa 
rto  15 


Anterior  pyramids 


Crossed  pyramidal 
tract.     Figs.  ]4- 


60 


ARCHITECTURE    OF    THE    BRAIN. 


Roots  o£  tlie 
seventh  nerv 
Figs.  8-9-10. 


Roots  of  tlie  hypo- 
between  the  olive 
and  pyramid. 


Olivary  body. 
Figs.  9  to  14. 


Dlivary  fasci( 
Fig.  12. 


Near  the  lower  extremity  of  the  olive,  the  pyramid  gives 
off  from  its  outer  side  a  small  tract  of  fibres,  which  arch  be- 
neath the  olive  and  across  the  surface  of  the  medulla  to  the 
restiform  body.  These  fibres  join  the  restiform  body,  pass 
to  the  cerebellum,  and  are  called  the  arciform  fibres  of  the 
medulla.  They  are  probably  associated  fibres,  and  do  not 
belong  to  the  pyramidal  system  which  is  motor  in  function. 
Immediately  beneath  the  pons,  fibres  are  given  off  from  the 
inner  side  of  the  pyramid  which  enter  the  raphe  to  decus- 
sate with  those  from  the  opposite  pyramid,  and  are  continu- 
ous on  the  floor  of  the  fourth  ventricle  with  the  roots  of  the 
seventh  nerve,  or  its  nucleus  of  the  opposite  side.  Below  the 
olive  other  fibres  enter  the  raphe  to  reach  the  opposite 
twelfth  nerve,  or  the  hypoglossal  nucleus. 

The  anterior  pyramid  is  bounded  above  externally  by  the 
olive,  from  which  it  is  separated, beneath  the  pons, by  a  sulcus, 
and  lower  down  by  a  slight  groove.  The  lower  portion  of 
the  pyramid  is  in  relation  externally  with  the  fundamental 
root  zone.  This  zone  above  is  buried  beneath  the  pyramid, 
between  the  olive  and  raphe. 

The  olive  is  an  oblong  body  situated  on  either  side 
of  the  medulla,  between  the  pyramid  and  the  lateral  tract,  or 
anterior  root  zone.  It  is  immediately  beneath  the  pons,  from 
which  it  is  separated  by  a  slight  groove.  This  body  is  about 
half  an  inch  in  length  from  above  downward,  and  one-fourth 
of  an  inch  across  its  middle.  Its  upper  extremity  is  con- 
nected with  a  large  tract  of  white  fibres  which  go  to  form  the 
anterior  layer  of  the  fillet  proper,  and  is  called  the  olivary 
fasciculus  of  the  fillet.  The  olivary  fasciculus  is  related  in 
front  with  the  fasciculus  of  the  fundamental  root  zone,  and 
behind  with  that  derived  from  the  lateral  tract  of  the  medulla, 
or   anterior  root  zone    of    the  cord.      The   olive   is    covered 


hilus 

connections  w 
the  tenth  and 
twelfth  nerves 


THK    MEDI'LLA    OBLONGATA    AND    SPINAL    CORD.  61 

externally  by  a  tliiu  layer  of  transverse  striie,  derived  from 
the  raphe,  which  passes  to  the  restiform  body  and  to  join 
the  commissure  of  the  flocculus.  These  are  probably  cere- 
bellar fibres  from  the  nuclei  in  the  floor  of  the  fourth  ventri- 
cle, belonging  to  the  same  system  as  the  uppermost  fibres  of 
the  pons  Varolii. 

A  transverse  section  of  the  olive  (figure  36)  shows  that  it  section  of  th 
is  composed  of  an  external  white  capsule,  within  which  is  a 
convoluted  layer  of  grey  matter  surrounding  a  mass  of  white 
subtance.  From  its  hilus,  which  is  above  and  internal  to  the  ^'s 
mass,  fibres  emerge  which  form  a  commissure  between  the 
opposite  olivary  bodies,  and  others  are  directed  backward  to 
the  floor  of  the  fourth  ventricle  to  connect  with  the  nuclei 
of  the  pneumogastric  and  hypoglossal  nerves.  The  upper 
part  of  the  olive  with  the  former,  and  the  lower  part  with 
the  latter  (Van  der  Kolk).  This  body  is  supposed  to  be 
concerned  with  the  co-ordination  of  the  muscles  of  speech. 

The  restiform  bodies,  or  inferior  peduncles,  connect  the 
cerebellum  with  the  medulla  and  spinal  cord.  They  arise 
from  the  posterior  and  outer  angles  of  the  medulla  upon  the 
sides  of  the  fourth  ventricle,  and  arch  upward  and  backward 
between  the  superior  and  middle  peduncles  of  the  cerebellum, 
to  spread  over  the  upper  surface  of  the  corpora  dentata,  iu 
which  they  terminate.  The  upper  border  of  the  restiform 
body  forms  the  posterior  side  of  the  restiform  triangle,  ami 
is  in  relation  to  the  parts  transmitted  by  the  triangle,  viz : 
the  anterior  root  of  the  eighth  nerve,  the  seventh  and  fifth 
nerves,  and  the  posterior  layer  of  the  fillet.  Its  posterior 
border  is  in  relation  Avith  the  posterior  root  of  the  eighth 
nerve  and  the  commissure  of  the  flocculus.  A  transverse 
section  through  the  restiform  nucleus  (figure  36)  shows  a  body 


Restiform  bod 


Restiforn 
and  pa 


62  ARCHITECTUEK    OF    THE    BRAIN. 

similar  but  larger  than  the  nucleus  of    the  olive,  and  that 
commissural  fibres  connect  the  opposite  nuclei. 
Restiform  system  The  Tcstiform  system  of  fibres  of  either  side  is  derived : 

oE  fibres.     Figs 

9-10.  from  the  restiform  nucleus  at  the  side  of  the  lower  extremity 

of  the  fourth  ventricle,  from  the  clavate  nucleus,  the  direct 
cerebellar  tract  of  the  cord,  the  arciform  fibres  of  the  an- 
terior pyramid,  the  cerebellar  fibres  from  the  floor  of  tlie 
fourth  ventricle  derived  from  the  raphe,  and  from  the  upper- 
most fibres  of  the  pons  Varolii,  which  proceed  from  the  raphe 
and  floor  of  the  fourth  ventricle. 


RECAPITULATION  OF  THE  TRACTS  OF  THE 
CEREBRO  SPINAL  AXIS. 


In  the  foregoing  pages  we  have  studied  the  several  parts 
of  the  cerebro-spinal  axis  in  segments,  and  have  connected 
each  by  its  immediate  relations,  and  by  the  continuity  of 
the  tracts  of  which  it  is  composed. 

It  will  now  be  of  advantage  to  review  the  axis  as  a  whole, 
and  to  trace  its  tracts  in  continuity  through  its  entire  extent, 
in  connection  with  the  nerve  centers  with  which  they  are 
associated.  In  so  doing,  we  will  attempt  to  arrange  the 
several  tracts  and  nerve  centers  into  general  systems,  to  accord 
with  their  supposed  functions,  in  order  to  assist  the  memory 
in  retaining  a  knowledge  of  the  anatomy,  and  to  simplify 
what  at  first  sight  appears  difficult  to  the  student. 

Beginning,  therefore,  with  the  spinal  cord,  we  will  follow 
each  system  from  its  origin  below  to  its  destination  above. 

The  ventricular  system  begins  as  a  minute  canal,  extend- 
ing through  the  length  of  the  spinal  cord  and  terminating 
above  in  the  fourth  ventricle,  at  the  middle  of  the  posterior 
surface  of  the  medulla  oblongata.  The  fourth  ventricle  is  a 
broad  cavity,  situated  behind  the  upper  half  of  the  medulla 
and  the  pons  Varolii.  At  its  upper  extremity  the  fourth  ven- 
tricle is  contracted  into  a  small  canal,  the  iter,  or  aquaduct  of 
Sylvius.  The  iter  is  about  three-fourths  of  an  inch  in  length, 
lies  beneath  the  upper  extremity  of  the  valve  of  Vieussens,  the 
commissure  of  the  corpora  quadrigemina,  and  the  jiosterior 
commissure  of  the  third  ventricle.     The  iter  terminates  above 


64 


ARCHITECTURE    OF    THE    BRAIN. 


sure   of    Bichat 
nd  foramina  of 


Lateral    ventricles 


Fifth  ventricle 


Infundibulum  and 

c: 

ivity  in  the 

P 

ituitary  body. 

Co  I 

nmunications 

w 

ith    tbe    sub- 

a 

tachnoid 

in  the  third  ventricle.  The  third  ventricle  is  a  vertical  cavity 
between  the  thalami  optici,  extending  from  the  base  of  the 
brain  to  the  fornix  above,  and  laterally,  upon  each  side,  to  the 
edges  of  the  fornix  where  it  communicates  with  the  lateral 
ventricles  through  the  fissure  of  Bichat  and  the  foramina  of 
Monro.  The  lateral  ventricles  are  large  cavities  in  the  hem- 
ispheres of  the  cerebrum,  and  each  ventricle  sends  projections 
into  the  frontal,  temporal,  and  occipital  lobes,  called  the  an- 
terior, middle  and  posterior  cornua  of  the  lateral  ventricles. 
The  fifth  ventricle  is  enclosed  by  the  two  layers  of  the  sep- 
tum lucidum,  and  has  no  communication  with  the  other  cavi- 
ties of  the  brain.  The  floor  of  the  third  ventricle  is  con- 
nected with  a  cavity  in  the  pituitary  body  by  a  canal  through 
the  infundibulum. 

The  ventricular  system  communicates  with  the  subarach- 
noid spaces  along  the  great  transverse  fissure,  and  by  a 
foramen  in  the  pia  mater  above  the  calamus  scriptorius, 
called  the  foramen  of  Majendie. 

The  ganglionic  system:  The  grey. matter  of  the  spinal 
cord  is  disposed  in  two  columns,  one  on  each  side,  enclosed 
by  the  white  matter  of  the  cord.  These  columns  are  united 
by  a  grey  commissure,  which  contains  in  its  middle  the  cen- 
tral canal  of  the  cord,  and  they  are  projected  forward  and 
backward  into  cornua,  which  are  the  origins  of  the  roots 
of  the  spinal  nerves.  The  anterior  horns  of  grey  mat- 
ter are  motor  in  function,  and  the  posterior  horns  contain  the 
centers  of  the  sensory  roots  of  the  spinal  nerves.  The  sens- 
ory roots  are  associated  with  the  sympathetic  nervous  system 
by  ganglia,  near  their  insertion  into  the  spinal  cord.  The 
vesicular  columns  of  Clarke  extend  along  the  junction  of  the 
posterior  cornua  and  the  posterior  surface  of  the  grey  com- 
missure, one  on  each  side  ot  the  posterior  median  fissure  of 


RECAPITULAriON  OF  THE  TRiiCTS  OF  THE  CERERRO  RPTNAL  AXIS.   65 


the  cord.  The  anterior  horns  of  the  grej-  matter  are  inter- 
rupted at  the  upper  extremity  of  the  spinal  cord  by  the 
decussation  of  the  crossed  pyramidal  tracts,  and  above  the 
decussation  they  gradually  approach  the  median  line  of  the 
medulla,  while  the  posterior  horns  gradually  diverge  or  are 
turned  outward. 

In  the  fourth  ventricle  the  grey  columns  are  exposed  upon 
its  floor  to  form  the  fasciculi  teretes;  the  motor  nerve  centers 
being  disposed  internally  along  the  sides  of  the  median  fis- 
sure, and  the  sensory  centers  upon  the  outer  sides  of  the  ven- 
tricle. The  grey  matter  above  the  fourth  ventricle  encloses 
the  iter,  and  contains  the  centers  that  control  the  movements 
of  the  eyes.  Above  the  iter,  it  spreads  upon  the  sides  and 
the  floor  of  the  third  ventricle;  and  the  sides  of  the  ventricle 
are  united  in  the  center  by  the  grey  or  middle  commissure  of 
the  third  ventricle.  On  the  floor  of  the  ventricle  the  grey 
matter  is  continuous  with  the  tuber  cinereum,  infundibulum, 
and  pituitary  body,  and  in  front  with  the  lamina  cinerea  and 
grey  matter  of  the  hemispheres. 

The  greater  ganglia  of  the  cerebro-spinal  axis  are  :  the 
hemispherical,  and  the  external  and  internal  basal  ganglia,  of 
the  cerebrum  ;  the  hemispherical  ganglia,  the  corpora  dentata 
and  the  ganglia  of  the  pons  Varolii,  or  the  internal  and 
external  basal  ganglia,  of  the  cerebellum. 

The  lesser  ganglia  are  :  the  olivary  bodies,  restiform  and 
clavate  nuclei,  of  the  medulla  oblongata ;  the  locus  niger,  cor- 
pora quadrigemina,  pineal  body,  the  geniculate  bodies,  the 
corpora  albicautia,  and  the  red  nuclei,  in  and  about  the  crura 
cerebri. 

Other  cerebral  ganglia  are:  the  claustrum,  and  the  substan- 
tia perforata.  The  olfactory  bulbs,  though  situated  in  the 
cranial  cavity,  may  properly  be  classed  with  the  spinal  ganglia. 


Fasciculi  teretes. 


Greater  ganglia. 


Claustrum.  sub- 
stantia perfor 


White  substance 
the  spinal  cord 


66  ARCHITECTUltE    OF    THE    BRAIN. 

Of  the  wliite  substance  of  the  spinal  cord,  the  fasciculi 
of  which  it  is  composed  are  rearranged  as  they  j)ass  upward 
through  the  several  portions  of  the  central  nervous  system, 
and  are  associated  with  the  grey  masses  above  mentioned.  The 
direct  pyramidal  tract,  and  the  crossed  pyramidal  tract  of  the 
opposite  side  of  the  spinal  cord,  unite  to  form  the  anterior 
pyramid  of  the  medulla  oblongata.  The  anterior  pyramid 
enters  the  pons  Varolii  and  is  associated  with  the  reticulated 
layer  of  the  anterior  portion  of  that  body.  This  layer  of 
the  pons  has  been  described  as  being  connected  above  with 
the  crusta  of  the  crura  cerebri,  and  laterally  with  the  deep 
layer  of  the  middle  peduncles  of  the  cerebellum.  It  also  con- 
tains a  large  amount  of  vesicular  matter,  and  is  the  ganglion 
of  the  pons  Varolii.  The  crusta  is  the  continuation  of  the 
pyramidal  tract  above  the  pons,  much  enlarged  by  an  accession 
of  fibres  from  this  body,  and  is  distributed  to  the  lenticular 
nucleus,  and  through  the  internal  capsule,  to  that  part  of  the 
hemispherical  ganglion  situated  about  the  fissure  of  Rolando, 
which  is  the  motor  area  of  the  hemisphere.  The  fibres  de- 
rived from  the  crusta  occupy  the  middle  portion  of  the  inter- 
nal capsule.  The  entire  tract  with  its  associations,  just 
described,  constitute  the  motor  system  of  the  cerebro-spinal 
axis. 

The  fundamental  root  zone  lies  upon  the  outer  side  of  the 
direct  pyramidal  tract  in  the  cord,  and  in  the  medulla  as  far 
as  the  lower  extremity  of  the  olive,  where  it  passes  inwards 
beneath  the  the  anterior  pyramid  between  the  olive  and 
the  raphe.  Above  the  olive,  it  spreads  out  into  a  thin  layer 
of  fibres  which  crosses  the  fillet  obliquely  in  an  outward 
direction  to  the  upper  border  of  the  middle  peduncle  of  the 
cerebellum,  where  it  becomes  superficial  upon  the  anterior 
part  of  the  outer  surface  of   the  superior  peduncle,  or  pro- 


RECAPITULATION  OF  THE  TEA0T9  OF  THE  CEREBRO  SPINAL  AXIS.    67 

cessus,  and  terminates  in  the  testes  and  brachium  posterius. 
These  tracts,  one  on  each  side,  might  with  propriety  be  called 
the  posterior  peduncles  of  the  corpora  quadrigemina,  and  it 
is  probable  that  through  them,  movements  of  the  body,  and 
the  maintenance  of  the  equilibrium,  are  directed  by  vision. 
Possibly  it  is  the  function  of  the  nates  to  direct  the  move- 
ments of  the  eyes  to  accommodate  the  vision  to  the  attitudes 
of  the  body  and  the  movements  of  an  object,  and  of  the 
testes  to  regulate  the  actions  of  the  muscles  to  avoid  a  blow 
or  to  grasp  an  object. 

The  fundamental  root  zones,  the  corpora  quadrigemina, 
brachia,  corpora  geniculata,  the  grey  matter  around  the  iter 
and  the  optic  tracts  together  constitute  a  visual  reflex  system. 

The  anterior  root  zone,  on  either  side,  is  divided  from  the 
fundamental  root  zone  by  the  anterior  roots  of  the  spinal 
nerves.  It  joins  the  fillet  of  the  pons,  in  which  it  lies  between 
the  olivary  fasciculus  in  front,  and  the  fillet  fibres  derived 
from  the  floor  of  the  fourth  ventricle,  behind.  In  the  crus 
cerebri,  the  fillet  is  internal  to  the  crusta,  from  which  it  is 
separated  by  the  substantia  nigra.  In  the  crus,  it  is  related 
internally  below  with  the  processus  of  the  same  side 
previous  to  its  decussation,  and  higher  up,  with  the  pro- 
cessus of  the  opposite  side  subsequent  to  its  decussation,  and, 
with  the  red  nucleus  of  the  tegmentum.  In  the  internal  cap- 
sule the  fillet  crosses  the  internal  surface  of  the  motor  tract 
in  an  oblique  direction,  beneath  the  thalamus,  and  in  front, 
lies  in  a  broad  groove  on  the  anterior  margin  of  the  internal 
capsular  fibres  of  the  crusta.  It  terminates  with  the  fillet 
fibres  derived  from  the  thalamus  in  the  frontal  lobe  of  the 
cerebrum. 

As  the  fillet  passes  upward  from  the  pons  Varolii  it 
receives  accessions  from  various  ganglia,  and  a  great  mass  from 


Cerebello-spinal 


68  ARCHITECTURE    OF   THE    BRAEN. 

the  thalamus,  which  unite  with  it  to  form  the  anterior  division 
©f  the  internal  capsule.  The  longitudinal  commissures  of 
the  cerebrum  unite  with  the  fillet  in  the  anterior  lobes  of  the 
brain,  and  with  it  constitute  the  fillet  system.  There  is  evi- 
dence to  support  the  theory,  that  the  fillet  is  the  perceptive 
system  through  which  the  mind  is  made  acquainted  with  its 
environments;  and,  through  the  medium  of  the  longtudinal 
commissures,  with  the  memories  of  things  and  the  events 
of  the  past,  which  have  been  laid  up  in  the  temporal  and 
occipital  lobes  of  the  brain. 

The  direct  cerebellar  tract  of  the  spinal  cord  originates 
in  the  vesicular  column  of  Clarke,  occupies  the  outer  side  of 
the  cord,  medulla  and  restif  orm  body,  and  with  the  latter  passes 
into  the  cerebellum.  It  probably  assists  in  the  formation  of 
a  cerebello-spinal  system,  which  is  concerned  in  the  function 
of  nutrition. 

The  posterior  median  columns  are  continued  in  the  me- 
dulla by  the  posterior  pyramids,  and  terminate  in  the  clavate 
nuclei,  beyond  which  their  connections  are  uncertain.  If 
these  columns  are  respiratory  tracts,  as  supposed  by  some  au- 
thorities, they  probably  form  an  arc  with  the  fifth  and  pneumo- 
gastric  nerves,  through  which  the  muscles  of  respiration  are 
co-ordinated  and  brought  into  action.  Until  corrected,  we 
will  class  this  tract  and  its  associations  as  a  respiratory 
system. 

The  posterior  root  zone,  or  Burdach's  column,  lies  external 
to  the  posterior  median  column,  and  behind  the  posterior 
horn  of  the  grey  matter  of  the  cord  and  the  lower  half  of  the 
medulla.  This  column  terminates  above  in  the  restiform 
nucleus,  and  is  continued  by  the  restiform  body  to  the  dentate 
nucleus  of  the  cerebellum.      It  is  associated  by  the   corpus 

Organ:c  and  mem-  •'  a 

ory  system.  dcutatum  wlth  thc  cerebellum  behind,  and  above,  by  the  pro- 


Reflex  respiratory 


EECAPITDLATION  OP  TAE  TAAOTS  OF  THE  CEREBEO  SPINAL  AXIS.   69 

cessus  with  the  opposite  red  nucleus,  thalamus,  and  hemis- 
phere of  the  cerebrum.  The  association  formed  by  this  tract 
in  conjunction  with  the  cerebellum,  and  the  temporal  and 
occipital  lobes  of  the  cerebrum,  including  the  intermediate 
tracts  and  grey  masses,  constitutes  the  organic  and  memory 
system. 

Thus  the  columns  of  the  spinal  cord  are  associated  into 
six  systems,  having  distinct  functions,  which  are  co-ordinated 
at  various  points  by  vesicular  masses  that  unite  the  several 
systems  into  one  great  function,  comprehended  in  the  word 
mind. 

The  reader  is  here  cautioned  against  accepting,  without 
due  reflection  and  investigation,  the  theories  advanced  in  rela- 
tion to  the  function  of  the  tracts  described  and  associated 
into  systems.  This  has  been  done  for  the  purpose  of  assist- 
ing the  memory  in  retaining  the  anatomical  relations. 


CENTRAL  ORIGIN  AND  RELATION  OF  THE 
CRANIAL  NERVES. 


First  nerve  - 
Olfactory. 


The  cranial  nerves  are  twelve  in  number  and  are  enumer- 
ated from  before  backward,  as :  first,  the  olfactory,  which  con- 
sists of  the  olfactory  bulb,  and  nerve  or  commissure,  which  is 
lodged  in  the  olfactory  fissure  upon  the  orbital  surface  of  the 
frontal  lobe  of  either  hemisphere  of  the  brain,  parallel  with 
the  anterior  median  fissure  of  the  cerebrum.  The  nerve 
divides  behind  into  three  roots,  external,  middle,  and  internal. 
The  external  root  crosses  the  outer  part  of  the  anterior  per- 
forated space  to  the  temporal  lobe  of  the  hemisphere,  the 
lower  portion  of  which  is  supposed  to  be  the  cerebral  center 
of  taste  and  smell.  The  middle  root  dips  into  the  anterior 
perforated  space,  and  apparently  passes  backward  to  the 
anterior  commissure  of  the  third  ventricle.  In  the  mole, 
an  animal  in  which  the  sense  of  smell  is  highly  developed, 
this  root  is  large  and  appears  to  decussate  with  its  fellow  in 
the  median  line,  and  passes  with  the  commissure  to  the  tem- 
poral lobe  of  the  opposite  hemisphere.  The  internal  root  pas- 
ses inward  behind  the  anterior  extremity  of  the  marginal  con- 
volution and  is  lost  in  the  median  fissure,  probably  forming, 
with  the  internal  root  of  the  opposite  nerve,  the  commissure 
between  the  olfactory  bulbs.  The  connection  of  the  anterior 
commissure  of  the  third  ventricle  with  the  opposite  temporal 
lobes  renders  it  probable  that  its  function  is  a  commissure  be- 
tween the  cerebral  centers  of   smell  of  the  opposite  hemi- 


CENTRAL  ORIGIN  AND  RELATION  OF  THE  CRANIAL  NERVES.       71 

spheres.     The  central  arrangement  of  the  olfactory  nerves,  if 
the  above  is  correct,  is  similar  to  that  of  the  optic  nerves. 

The  second,  or  optic  nerves  of  each  side,  unite  to  form     second  nerve- 

jI  ,•  •  ^  *  T     *  ^        ,  -,  .  Optic.     Figs,  2- 

the  optic  commissure,  and  again  divide  into  the  optic  tracts.  9-10  to  1-1,  u*. 
Each  tract  winds  upon  the  external  surface  of  the  cerebral 
peduncle,  near  the  posterior  part  of  which  it  divides  into  two 
tracts  which  terminate:  the  inferior,  in  the  internal  geniculate 
body;  and  the  superior,  a  larger  tract,  in  the  external  genicu- 
late body  and  pulvinar  of  the  thalamus.  The  divisions  of  the 
optic  tract  are  connected  with  the  corpora  quadrigimina  by 
the  brachia,  anterius  and  posterius.  The  posterior  fibres  of 
the  optic  commissure  are  commissural  between  the  cerebral 
nerve  centers,  the  middle  fibres  decussate,  the  anterior  fibres 
are  commissural  between  the  retinfe,and  the  external  fibres  of 
each  nerve  are  continued  into  the  tract  of  the  same  side. 

The  third  nerve,  motor  occuli,  arises  from  the  inner  side 
of  the  crus  cerebri  near  the  bottom  of  the  posterior  perforated 
space.  It  pierces  the  internal  margin  of  the  crusta,  and  upon 
entering  the  tegmentum,  its  fibres  spread  into  numerous  striae 
as  they  pass  through  the  anterior  extremity  of  the  processus, 
to  their  destination  in  the  grey  matter  beneath  the  iter. 

The  fourth  nerve,  pathetic,  arises  from  the  inner  margin 
of  the  processus,  behind  the  testes,  and  is -connected  with  the 
grey  matter  surrounding  the  iter  which  lies  immediately 
beneath  its  apparent  origin. 

The  fifth  nerve,  the  trigeminus,  arises  from  the  center  of     Fifthnerve- 

Trigeminus. 

the  side  of  the  pons  Varolii.  It  transfixes  the  middle  pedun-  Figs.  7-9-10-13. 
cle  of  the  cerebellum  as  it  passes  obliquely  backward,  out- 
ward, and  downward  to  the  inferior  angle  of  the  restiform  trian- 
gle, through  which  it  reaches  the  gi'ey  matter  beneath  the 
floor  of  the  fourth  ventricle.  It  divides  into  several  slips 
which  are  distributed  to  several  grey  nuclei  as  far  down  as 


Motor  occu 
Figs.  7-9-27 


Pathetic.     Figs. 


72 


ARCHITECTURE    OF    THE    BRAIN. 


Sixth  n 
Abdu 


Eighth  nerv 
Auditory, 
to  10. 


the  calamus  scriptoiius.  Its  motor  root  is  small,  aud  at  its 
origin  is  above  and  behind  its  sensory  root. 

The  bixth  nerve,  the  abducent,  lies  upon  the  pons,  and, 
winding  beneath  the  lower  margin  of  this  body,  passes  out- 
ward above  the  olive  to  join  the  fillet  at  its  outer  margin, 
where  it  is  in  relation  with  the  fifth,  seventh,  and  anterior 
root  of  the  eighth  nerves.  Above,  it  leaves  the  fillet  to 
reach  the  grey  matter  in  the  floor  of  the  iter. 

The  seventh  nerve,  facial,  arises  below  the  middle  pedun- 
cle of  the  cerebellum,  internal  to  the  flocculus  and  the  audi- 
tory nerve,  and,  passing  upward  behind  the  middle  peduncle, 
between  the  restiform  body  and  the  outer  margin  of  the 
fillet,  it  enters  the  fourth  ventricle  through  the  anterior  angle 
of  the  restiform  triangle.  It  crosses  the  floor  of  the  ventricle 
obliquely  downward  and  inward  to  the  raphe,  where  it  decus- 
sates with  the  opposite  nerve  and  joins  the  anterior  pyramid 
of  the  opposite  side  beneath  the  lower  margin  of  the  pons. 
In  the  floor  of  the  fourth  ventricle  it  is  connected  with  the 
nucleus  of  the  seventh  nerve.  It  forms  the  superior  striae 
transverse  of  the  floor  of  the  fourth  ventricle. 

The  eighth  nerve,  auditory,  lies  beneath  the  lower  margin 
of  the  middle  peduncle  of  the  cerebellum,  between  the 
seventh  nerve  and  the  flocculus.  It  divides  behind  into  two 
roots,  an  anterior  and  posterior,  which  embrace  the  restiform 
body.  The  anterior  root,  in  conjunction  with  tlie  seventh 
nerve,  passes  through  the  restiform  triangle,  occupying  its 
superior  angle,  to  reach  the  floor  of  the  fourth  ventricle, 
where  it  joins  the  posterior  tract  of  the  fillet,  and  passes 
downward  on  the  inner  side  of  the  restiform  body,  to  reach 
the  auditory  nucleus.  The  posterior  root  passes  inward 
beneath  the  arch  of  the  restiform  body,  and  across  it  to  the 
floor  of  the  fourth  ventricle,  upon  which  it  forms  the  inferior 
striae  transversse.     This  root  divides  into  striae,  which  are  lost 


CENTRAL  OEIGLN  AND  RELATION  OF  THK  CRANIAL  NERVES. 


7S 


in  the  raphe,  and  is  connected  with  the  arciform  fibres,  and 
the  commissure  of  the  flocculus.  It  is  probable  that  the 
roots  of  the  auditory  nerve  have  the  same  disposition  as 
those  of  the  olfactory  and  the  optic  nerves,  and  possibly  this 
arrangement  is  common  to  the  roots  of  all  the  sensory  nerves. 

The  ninth  nerve,  glosso-pharingeal,  lies  beneath  the  floc- 
culus above  the  pneumogastric  nerve,  and  passes  inward 
behind  the  olive  to  the  floor  of  the  fourth  ventricle,  where  it 
is  connected  with  its  nucleus. 

The  tenth  nerve,  or  pneumogastric,  is  beneath  the  ninth, 
passes  inward  behind  the  olive  to  the  floor  of  the  fourth  ven- 
tricle. Its  nuclens  is  connected  with  the  upper  part  of  the 
olive  by  a  commissure. 

The  eleventh  nerve,  spinal  accessory,  arises  by  slips  from 
the  lateral  tract  of  the  spinal  cord  as  low  as  the  sixth  or 
seventh  cervical  vertibrae,  and  from  the  side  of  the  medulla, 
which  unite  into  a  trunk  that  lies  behind  the  flocculus  and 
the  pneumogastric  nerve.  Its  deep  origin  is  from  the  anterior 
horns  of  the  grey  matter  of  the  cord. 

The  twelfth  nerve,  hypoglossal,  arises  from  between  the 
olive  and  anterior  pyramid  of  the  medulla.  Its  roots  pass 
backward  between  the  olive  and  the  fundamental  root  zone  to 
the  floor  of  the  fourth  ventricle.  Its  nucleus  is  connected  with 
the  lower  part  of  the  olive  and  with  the  opposite  anterior 
pyramid. 


Eleventh  nerve — 
Spinal  accessory.' 
Fig.  7. 


Twelfth  1 
Hypoglossal. 
Fig.  7. 


74  ARCHITECTURE    OF    THE    BRAIN. 


Figure  1.  The  appearance  of  the  upper  purface  of  the 
cerebrum,  and  the  convolutions  and  fissures  marked  upon 
it.  The  great  longitudinal  fissure  separates  the  hemispheres. 
The  convolutions  are  named,  and  the  fissure  of  Rolando  indi- 
cated upon  the  left  hemisphere;  and  the  three  great  functions 
of  the  brain  are  located  upon  the  right.  The  superior  ex- 
tremities of  the  calloso-marginal  and  pareto-occipital  fissures 
are  marked  at  their  terminations  as  they  emerge  from  the 
longitudinal  fissure;  the  former  immediately  behind  the  upper 
extremity  of  the  fissure  of  Rolando,  corresponding  to  a  point 
just  behind  the  vertex  of  the  skull;  and  the  latter  to 
a  point  beneath  the  superior  angle  of  the  occipital  bone, 
and  the  crown  of  the  head.  By  reference  to  figure  26, 
it  will  be  seen  that  the  parieto-occipital  and  calloso-mar- 
ginal fissures  form  the  boundaries  of  certain  lobes  upon 
the  inner  surface  of  the  hemisphere,  the  upper  borders  of  these 
lobes  occupy  the  spaces  indicated  in  this  plate  upon  the  mar- 
gin of  the  longitudinal  fissure.  The  cuneus  is  located  upon 
surface  of  the  head,  by  a  space  extending  along  the  median 
line  from  the  occiput  to  the  crown;  the  quadratus — from  the 
crown  almost  to  the  vertex;  the  paracentral  lobule — from  the 
vertex  to  a  point  an  inch  and  a  half  in  front  of  it,  and  the 
marginal  convolution  completes  the  distance  to  the  nasion. 


Figure  1. 


76  ARCHITECTUEB    OF    THE    BRAIlSr. 

Figure  2.  Base  of  tlie  cerebrum: — divided  into  two 
surfaces,  orbital  and  temporo-occipital.  The  whole  surface 
is  divided  into  lateral  halves  from  before  backward  by  (1)  the 
anterior  median  fissure,  (2)  the  interpeduncular  space,  (3)  the 
oval  hilus  of  the  cerebrum,  (4)  the  posterior  median  fissure. 
Each  lateral  half  has  three  lobes,  the  frontal,  and  the  tem- 
poral, separated  by  the  fissure  of  Sylvius,  and  behind, 
the  occipital  lobe.  On  each  side  of  the  anterior  median  fissure 
are  the  olfactory  fissures,  bulbs  and  nerves.  Each  nerve  ter- 
minates posteriorly  in  three  roots,  external,  middle  and 
internal.  The  space  between  the  temporal  lobes  contains 
from  before  backward:  (1)  lamina  cinerea,  obscured  by  the 
optic  commissure,  (2)  optic  nerves  commissure  and  tracts,  (3) 
the  anterior  perforated  spaces,  one  on  each  side  of  the  optic 
commissure,  and  leading  outward  from  these  spaces  are 
the  fissures  of  Sylvius,  (4)  enclosed  by  the  optic  tracts  and 
the  crura  cerebri  are:  the  tuber  cinereum,  infundibulum  and 
pituitary  body,  corpora  albicantia,  posterior  perforated  space, 
and  third  nerves.  In  the  hilus  of  the  cerebrum  are  seen:  (1) 
in  the  middle  line  the  third  ventricle,  its  anterior,  middle  and 
posterior  commissures, — the  anterior  and  middle  commissures 
are  not  visible  in  the  figure, — (2)  the  pineal  body,  (3)  the 
splenium  and  lyra  of  the  corpus  callosum.  On  each  side  of 
the  middle  line  is  the  ruptured  end  of  a  crus  cerebri  or  pe- 
duncle. The  outer  side  of  the  broken  surface  of  the  peduncle 
shows:  (1)  the  crusta,  (2)  in  front,  the  fillet,  (3)  midway,  the 
bed  of  the  red  nucleus,  behind  which  are  (4)  the  ruptured 
fibres  of  the  brachia  of  the  corpora  quadrigemina,  and  (5) 
the  posterior  extremity  of  the  thalamus  opticus  or  pulvinar. 

On  the  margins  of  the  posterior  median  fissure  are  (1) 
the  posterior  extremity  of  the  gyrus,  (2)  parieto-occipital  fissure, 
and  (3)  the  lobus  lingualis.  " 

The  convolutions  seen  on  this  sui'faee  can  be  read  upon 
the  plate. 


Figure  2. 


78  AKCHITECTUBE    OF    THE    BEAUT. 

Figure  3.  The  upper  portion  of  the  cerebrum  is  removed 
to  a  level  with  the  corpus  callosum.  This  body  forms  a  wide 
furrow  in  the  middle  of  the  surface  exposed,  and  is  concave 
from  side  to  side.  Upon  each  side  of  the  corpus  callosum  is  a 
crest  extending  into  the  anterior  and  posterior  lobes  of  each 
hemisphere,  which  is  the  line  of  decussation  of  the  corpus  callo- 
sum with  the  internal  capsule.  Internal  to  the  crest,  on  each  side, 
is  the  superior  longitudinal  commissure,  or  commissure  of  the 
gyrus,  connecting  the  occipital  and  frontal  lobes,  represented 
on  the  left  side  of  the  figure.  In  the  center  of  the  corpus 
callosum  is  the  raphe,  upon  each  side  of  which  are  two 
longitudinal  white  lines,  the  stria3  longitudinales  or  nerves 
of  Lancisci.  The  corpus  callosum  is  surrounded  by  the 
corona  radiata,  or  white  substance,  in  which  are  seen  numer- 
ous punctate  spots  or  torn  vessels,  the  puncta  vasculosa. 
The  corona  is  bounded  externally  by  grey  matter,  the  hemis- 
pherical ganglia,  which  is  divided  in  front  and  behind  by  the 
anterior  and  posterior  median  fissures,  at  the  bottom  of  which 
are  lateral  extensions,  called  the  ventricles  of  the  corpus  cal- 
losum. Behind  the  posterior  margin  of  the  corpus  callosum 
are,  the  gyrus,  and  the  exposed  anterior  surface  of  the  cuneus. 
On  the  lateral  margins  of  the  hemispheres  are  the  posterior 
extremities  of  the  fissures  of  Sylvius,  and  a  triangle  is  drawn 
upon  the  right  side  of  the  figure  to  illustrate  the  inter- 
nuncial  fibres,  and  the  external  longitudinal  commissure  ;  the 
former  connecting  the  centers  of  word  and  sight  mem- 
ories, and  the  latter  associating  these  centers  with  that 
of  speech.  In  front  of  the  fissure  of  Sylvius  is  a  scheme 
representing  the  tracts  for  automatic  movements  of  the 
hand  produced  by  visual  and  aural  impressions;  and  still 
more  anterior,  a  tract  connecting  the  center  for  movements  of 
the  hand  with  the  speech  center,  through  which  the  latter 
center  may  be  excited  by  movements  of  the  hand,  in  the  event 
of  a  lesion  of  the  direct  tracts  between  the  aural  and  visual 
memories  and  the  speech  center. 


FK'ure  3. 


80  ARCHITECTURE    OF    THE    BRAIN. 

Figure  4.  Fornix  and  lateral  ventricles.  In  the  median 
line  from  before  backwards  are:  (1)  the  anterior  median  fissure 
at  the  posterior  extremity  of  which  is  a  lateral  fissure,  the 
ventricle  of  the  corpus  callosum,  (2)  the  genu  of  the  corpus 
callosum,  (3)  septum  lucidum,  containing  the  fifth  ventricle, 
(4)  the  fornix,  the  anterior  pillars  of  which  bending  down- 
ward bound  the  foramena  of  Monro  in  front;  upon 
the  upper  surface,  in  the  median  line,  is  an  elevated  ridge 
which  forms  the  attachment  of  the  fornix  to  the  under  surface 
of  the  corpus  callosum,  (5)  the  splenium  of  the  corpus  cal- 
losum, posterior  to  which  is  a  part  of  the  ventricle  of  the 
corpus  callosum,  and  (6)  the  posterior  median  fissure. 

On  each  side  of  the  median  line  are  the  lateral  ventricles, 
basal  ganglia  and  internal  capsules,  corona  radiata  and  the 
hemispherical  ganglia.  The  lateral  ventricle  is  divided,  into  a 
body,  an  anterior,  middle,  and  posterior  cornua.  The  ventricle 
is  bounded  externally  in  front  by  the  internal  capsule,  upon 
which  the  functions  of  its  parts  are  indicated.  Behind  the  cap. 
sule  is  a  broad  groove  leading  from  the  body  of  the  ventricle 
to  the  middle  and  posterior  cornua.  The  posterior  portion  of 
the  capsule  bends  downward  and  is  called  its  genu.  The  body 
of  the  ventricle  contains  from  within  outward;  (1)  the  fornix 
and  corpus  fimbriatum,  (2)  fissure  of  Bichat,  (3)  choroid 
plexus,  (4)  part  of  the  thalamus  opticus,  (6)  t^nia  semicircu- 
laris,  (6)  caudate  nucleus.  The  anterior  cornu  contains  the 
head  of  the  caudate  body;  the  middle  cornu,  the  hippocampus 
major,  and  pes  hippocampi;  the  posterior  cornu  contains  the 
hippocampus  minor;  and  between  these  cornua  is  the  pes  acces- 
sorius  or  eminentia  collateralis.  The  tail  of  the  caudate 
body,  taenia  semicircularis,  choroid  plexus,  and  corpus  fim- 
briatum descend  together  along  the  inner  margin  of  the 
middle  cornu  to  the  apex  of  the  ungual  convolution.  See 
Figs  5,  7,  17.  The  hemispherical  ganglia  constitute  the 
grej-  matter  which  encloses  the  corona  radiata. 


Figure  4. 


82  ARCHITECTURE    OF    THE    BRAIN. 

Figure  5.  A  horizontal  and  lateral  view,  with  the  foinix 
divided  and  reflected,  exposing  the  velum  interpositum.  In 
the  median  line  from  before  backward  are  seen:  (1)  the  anterior 
median  fissure,  (2)  genu  of  the  corpus  callosum,  (3)  septum 
lucidum  and  fifth  ventricle,  (4)  anterior  pillars  of  the  fornix, 
(6)  velum  interpositum,  triangular  in  shape,  fringed  by  the 
choroid  plexuses,  and  containing  the  vense  Galeni  and  choroid 
arteries,  and,  at  its  center  behind,  an  elevation  denoting  the 
position  of  the  pineal  gland.  (6)  Behind  the  velum  is 
the  reflected  fornix  and  corpus  callosum,  upon  which  are 
seen  transverse  striae,  the  lyra.  The  attachment  of  the 
fornix  to  the  corpus  callosum  is  seen  in  the  middle  of  the 
section  of  these  parts.  Behind  the  corpus  callosum,  is 
the  posterior  median  fissure.  The  parts  forming  the 
floor  of  the  lateral  ventricle,  as  well  as  the  internal  cap- 
sule, are  shown  in  figure  4.  The  oblique  view  presented 
by  this  figure  exposes  fully  the  middle  and  posterior  cornua 
and  the  parts  contained  in  them,  also  the  situation  and  extent 
of  the  corpus  fimbriatum,  transverse  fissure,  and  choroid 
plexus,  as  well  as  the  manner  in  which  they  encircle  behind 
the  genu  of  the  internal  capsule  into  the  middle  cornu. 
A  complete  view  of  the  pes  hippocampi  and  pes  accessorius  is 
ex|)08ed.  At  the  lower  and  anterior  extremity  of  the  middle 
cornu  is  a  transverse  section  of  the  lenticular  nucleus,  external 
capsule,  claustrum,  insula  and  Sylvian  fissure.  Below  the 
lenticular  body,  or  external  basal  ganglion,  is  a  tract  of 
transverse  fibres,  which  is  a  section  of  the  inferior  ramus  of 
the  internal  capsule.  See  figure  7.  The  inferior  ramus  of 
the  internal  capsule  forms  the  roof  of  the  middle  cornu.  In 
the  roof  of  the  middle  cornu  which  has  been  removed  in  this 
dissection  are  the  taenia  semicircularis  and  the  tail  of  the  cau- 
date nucleus  lying  parallel  to  the  optic  tract.     See  figure    7. 


Figure  5. 


84  ARCHITECTURE    OP    THE    BRAIK. 

Figure  6.  In  this  dissection,  the  velum  interj^ositum  and 
the  right  occipital  and  temporal  lobes  are  removed,  exposing 
the  third  ventricle,  pineal  gland,  corpora  quadrigemina,  basal 
ganglia,  and  the  upper  surface  of  the  cerebellum.  Figure  7 
is  a  lateral  view  of  the  same  dissection,  and  shows  the  relation 
of  the  external  basal  ganglion,  or  lenticular  nucleus,  to  the 
internal  capsule;  also  the  posterior  extremities  of  the  caudate 
nucleus  and  t;^nia  semi-circularis,  as  they  descend  behind 
the  genu  of  the  internal  capsule  into  the  roof  of  the  middle 
coruu  of  the  lateral  ventricle. 

In  the  median  line  from  before  backward  (Fig.  6)  are 
seen:  the  anterior  median  fissure,  genu  of  the  corpus  callosum, 
septum  lucidum  enclosing  the  fifth  ventricle,  the  divided 
anterior  pillai's  of  the  fornix,  the  third  ventricle  containing 
three  commissures,  anterior,  middle,  and  posterior,  the  pineal 
gland  and  its  pillars,  corpora  quadrigemina  divided  into  four 
tubercles  by  a  crucial  depression,  the  incisui'a  anterio  of  the 
cerebellum,  the  superior  vermiform  process,  and  the  inclsura 
posterior.  Laterally:  in  front,  is  the  corona  radiata;  in  the 
middle,  the  internal  and  external  basal  ganglia,  separated  by 
the  internal  capsule;  and  behind,  the  upper  surface  of  a  lateral 
lobe  of  the  cerebellum,  made  up  of  the  lobus  quadratus  and 
the  posterior,  or  semilunaris  lobe.  The  internal  basal  ganglia 
are,  the  caudate  nucleus  and  the  thalamus  opticus,  divided 
by  the  taenia  semicircularis,  which  lies  in  a  depression  between 
them.  The  thalamus  is  composed  of  four  distinct  bodies; 
(1)  the  pison  (pea),  a  small  body  at  the  junction  of  the 
anterior  pillar  of  the  pineal  gland  with  the  body  of  the 
thalamus,  (2)  the  pulvinar,  pointed  in  front  opposite  the  mid- 
dle commissure,  and  continuous  behind  with  the  external 
geniculate  body  and  outer  division  of  the  optic  tract,  (3)  the 
tuberculum,  a  nodule  at  the  anterior  exteremity  of  the  thala- 
mus, continuous  with  a  slim  tract  of  white  fibres  directed  back- 
ward and  outward,  along  a  groove  on  the  upper  surface  of  the 
thalamus  which  lodges  the  corpus  fiimbriatum,  (4)  the  fusi- 
formis,  which  is  an  oblong  elevation  lying  on  the  outer 
border  of  the  thalamus,  internal  to  the  taenia  semicircularis. 


Figure  6. 


86  AECHirECTURE    OP   THE   BRAIN. 

Figure  7  is  a  lateral  and  inferior  view  of  the  same  dissection  as  figure  6, 
from  which  may  be  studied  on  the  right  of  the  figure  (left  side  of  the  brain) 
the  parts  seen  upon  the  base  of  the  brain.  On  the  left  side  of  the  figure 
are  seen;  the  tracts  of  the  medulla  oblongata,  the  expansion  of  the  crus 
cerebri  into  the  internal  capsule,  and  the  relation  of  the  capsule  to  the 
lenticular  nucleus,  to  the  optic  tract,  taenia  semicircularis,  and  tail  of  the 
caudate  nucleus.  The  pons  is  divided  to  show  the  descent  of  the  crusta, 
and  the  continuation  of  a  portion  of  its  fibres  into  the  anterior  pyramid 
of  the  medulla.  The  under  surface  of  the  cerebellum  is  also  exposed,  and 
in  conjunction  with  figure  6  the  parts  of  this  portion  of  the  brain  can  be 
studied.  The  following  parts  are  seen  on  the  base  of  the  brain  from 
before  backward  in  the  median  line :  (1)  anterior  median  fissure,  (2) 
lamina  cinerea  (hidden  by  the  optic  commissure),  (3)  optic  commissure, 
nerves  and  tracts,  (4)  interpeduncular  space,  bounded  by  the  optic  tracts 
and  cerebral  peduncles,  and  containing,  the  tuber  cinereum,  infundibulum 
and  pituitary  body  (removed),  corpora  albicantia,  posterior  perforated 
space  and  third  nerves,  (5)  the  pons  Varolii,  (6)  the  medulla  oblongata. 
On  the  outer  side  from  before  backward  are:  (1)  the  orbital  convolutions, 
(2)  olfactory  bulb,  and  nerve  terminating  in  three  roots,  (3)  the  anterior 
perforated  space,  upon  which  is  the  anterior  pillar  of  the  corpus  callosum 
(4)  the  fissure  of  Sylvius,  (5)  temporal  lobes,  (6)  crug  cerebri  and  fourth 
nerve,  (7)  great  transverse  fissure,  and  (8)  the  flocculus  and  under  surface 
of  the  cerebellum.  The  cranial  nerves  are  numbered  from  before  back- 
ward: 1st,  olfactory;  2nd,  optic;  3rd,  motor  oculi;  4th,  pathetic;  5th, 
trigeminus;  6th,  abducent;  7th,  facial;  8th,  auditory;  9th,  glosso-phar- 
yngeal;    10th,    pneumogastric ;    11th,    spinal  accessar}-;  12th,    hypoglossal. 

On  the  left  side  of  the  figure  behind,  is  the  incisura  posterior  and 
inferior  vermiform  process,  lobes  of  the  cerebellum,  tracts  of  the  medulla, 
arciform  fibres,  olive,  crusta,  optic  tract  and  geniculate  bodies,  and  the 
inferior  extremities  of  the  taenia  semicircularis,  tail  of  caudate  body 
ending  in  a  bulbar  extremity,  and  the  auricular  expansion  of  the  fibres  of 
the  internal  capsule  enclosing  the  lenticular  nucleus.  Upon  the  surface  of 
the  lenticular  body  is  a  fragment  of  the  external  capsule,  at  the  inner 
angle  of  which  is  (AC)  the  outer  extremity  of  the  anterior  commissure  of 
the  third  ventricle. 

The  internal  capsule  is  divided  into  four  parts :  the  anterior,  which 
is  hidden  by  the  frontal  lobe;  the  middle,  which  is  the  motor  portion;  the 
posterior,  containing  the  fibres  of  common  sensation  and  the  optic  radiation; 
and  inferior  ramus  of  the  capsule  to  the  temporal  convolutions,  which 
contains  the  tracts  of  hearing,  If  ste,  and  smell. 


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Figure  7. 


88  AKOHITEOTURE   OF   THE   BRAIN. 

Figure  8.  Figures  8  and  9  are  posterior  and  lateral  views  of  the  same 
dissection,  in  which  the  hemispheres  and  the  cerebellum  have  been  removed 
giving  a  complete  view  of  the  intermedia. 

This  figure  can  be  divided  into  three  sections:  a  superior  or  cerebral,  a 
middle  or  peduncular,  and  an  inferior  or  medullar} 

At  the  upper,  or  anterior  part  of  the  superior  division  is  a  part  of  the 
corpus  callosum  crossing  above  the  anterior  horns  of  the  lateral  ventricles, 
and  uniting  at  its  lateral  extremities  with  the  intei'ual  capsules.  The  corpus 
callosum  and  the  capsules  enclose,  as  in  a  triangle,  the  ventricles  and  the 
internal  basal  ganglia,  caudate  nuclei  and  thalami  optici.  The  caudate 
nucleus  of  the  left  side  has  been  removed  in  order  to  show  the  distri- 
bution of  fibres  from  the  thalamus  to  the  iuternal  capsule,  and  also  the 
fibres  which  emerge  from  between  the  lamiaa  of  the  capsule  to  reinforce  the 
taenia  semicircularis  as  it  passes  forward  into  the  anterior  horn  of  the  lateral 
ventricle.  The  fornix  lies  over  the  third  ventricle,  and,  in  its  middle  is 
joined  to  the  uuder  surface  of  the  corpus  callosum  by  the  septum  lucidum, 
which  contains  thefifth  ventricle, and  separatesthe  anterior  horus  of  the  lateral 
ventricles.  The  posterior  part  of  the  thalamus  winds  around  the  crus  cere- 
bri to  be  continuous  with  the  optic  tract.  The  opening  to  the  third  ventricle 
is  surrounded  by  the  pineal  body  and  its  anterior  peduncles,  and  upon  each 
side  in  the  front  of  the  pineal  body  is  a  small  tubercle  ot^  gi'^y  matter, 
called  the  pison.  At  the  posterior  extremity  of  the  thalamus  are  two  emi- 
nences, one  on  each  division  of  the  optic  tract,  the  corpora  geniculata, 
externum  and  internum.  Between  the  thalami  are  four  tubercles,  divided 
by  a  crucial  depression,  the  corpora  quadrigmina,  or  nates  and  testes.  Di- 
rected obliquely  outward  from  the  nates  and  testes  to  the  geniculate  bodies 
are  the  brachia,  anterius  and  posterius. 

The  middle  division  contains  from  within  outward:  the  valve  of 
Vieussens,  processes  and  fourth  nerves,  fundamental  root  zones  and  crustte. 
A  vertical  groove  upon  each  crus  cerebii  lies  between  the  root  zone  and 
the  crusta.  Lower  down,  on  either  side,  the  relations  of  the  parts  are  from 
the  median  line  outward:  the  valve  of  Vieussens,  processus,  corpus  denta- 
tum,  restiforni  body,  and  the  pons  Varolii.  These  latter  parts  form  an 
arch  or  roof  over  the  fourth  ventricle. 

The  inferior  division  is  broad  above,  and  flattened  beneath  the  arch 
formed  by  the  parts  just  mentioned,  where  it  presents  a  triangular  depressed 
surface  which  is  part  of  the  floor  of  the  fourth  ventricle.  This  surface  is 
crossed  by  the  roots  of  the  seventh  and  eighth  nerves,  the  stride  trausversse. 
In  the  median  line  is  the  posterior  median  fissure  of  the  fourth  ventricle, 
which  terminates  below  in  the  central  canal  of  the  spinal  cord,  and  is  con- 
tinuous with  the  posterior  median  fissure  of  the  medulla  oblongata.  Bound- 
ing the  sides  of  the  floor  of  the  fourth  ventricle  are  the  restif orm  bodies,  and 
at  the  apex  of  the  ventricle  are  two  eminences  on  each  side,  the  anterior  are 
the  restiform  nuclei,  and  the  posterior,  the  clavate  nuclei.  The  lower  portion 
of  this  division  is  rounded,  the  columns  of  which  it  is  constituted  are  sim- 
ilar to  those  of  the  spinal  cord,  a  section  of  which  is  seen  on  the  end. 


■     / 

\    J 


Figure  8. 


90  ARCHITECTURE    OF    THE    BRAIN. 

Figure  9.  For  the  convenience  of  description,  figure  9  may  be  divided  into  four 
portions:  cerebral,  peduncular,  pons,  and  medullary. 

In  the  center  of  the  cerebral  portion  is  the  lenticular  nucleus,  or  external  basal 
ganglion,  which  is  bounded  above  by  the  deep  fibres  of  the  external  capsule,  the  super- 
ficial fibres  having  been  removed  in  order  to  expose  the  ganglion.  The  external  capsule, 
is  derived  from  the  outer  surface  of  the  ganglion,  and  its  fibres  radiate  upwards  in  the 
middle,  and  in  front  and  behind,  they  are  directed  obliquely  forward  and  backward  (See 
Fig.  19).  Tbe  internal  capsule  receives  the  fibres  of  the  external  capsule,  radiates  forwaid 
where  it  is  called  the  fillet,  upward  in  the  middle,  which  are  its  motor  fibres,  and  behind 
and  below,  which  are  the  sensory  and  memory  divisions  of  the  capsule.  The  external  longi 
tudinal  commissure  extends  from  the  sensory  radiation  of  the  internal  capsule  to  its  fillet 
division,  which  it  joins  in  front  of  the  lenticular  nucleus.  The  commissure  lies  beneath  the 
lenticular  body  and  upon,  or  rather  within  the  inferior,  or  temporal  radiation  of  the 
internal  capsule.  Beneath  the  longitudinal  commissure  and  the  inferior  ramus  of  the 
internal  capsule  are,  from  behind  forward :  the  corpora  quadrigemina,  geniculate  bodies, 
the  upper  and  lower  divisions  of  the  optic  tract,  the  optic  tract  commissure  and  nerves, 
and  the  lamina  cinerea. 

The  peduncular  division  contains  from  behind  forward,  the  processus,  the  fourth 
nerve,  fundamental  root  zone,  vertical  groove,  crusta  cerebri,  and  interpeduncular  space 
containing  the  tuber  cinereum,  infundibulum,  corpora  albicantia,  posterior  perforated 
space  and  third  nerves.  The  latter  parts,  together  with  the  optic  commissure  and  lamina 
cinerea  form  the  floor  of  the  third  ventricle. 

The  region  of  the  pons  Varolii  contains  from  before  backwards:  (1)  the  superficial 
or  commissural  layer,  the  upper  fibres  of  which  are  derived  from  the  raphe  and  floor  of 
the  fourth  ventricle,  and  enter  the  cerebellum  along  with  the  restiform  body,  to  be  dis- 
tributed to  the  corpus  dentatum;  (2)  the  reticu'ated  layer,  or  formatio  reticularis  of  the 
pons,  composed  of  the  fibres  of  the  crusta,  anterior  pyramid  of  the  medulla,  and  the 
deep  layer  of  the  pons,  interspersed  with  grey  matter,  and  is  the  nucleus  of  the  pons,  or 
external  basal  ganglion  of  the  cerebellum;  (3)  the  fillet,  composed  of  four  layers:  funda- 
mental root  zone,  olivary  fasciculus,  anterior  root  zone,  fillet  tract  from  fourth  ventricle; 
(4)  the  fifth,  seventh  and  eighth  nerves,  which  pass  through  the  restiform  triangle  (see 
figures  10-12)  into  the  floor  of  the  fourth  ventricle,  the  roots  of  the  latter  two  nerves 
form  the  striae  transvorste  on  the  floor  of  the  ventricle  (figures  8-10) ;  the  sixth  nerve 
winds  beneath  the  pons  and  joins  the  fillet;  (5)  the  reflected  superior  portion  of  the 
arch  of  the  restiform  body,  corpus  dentatum  and  posterior  root  of  the  auditory  nerve. 

The  medulla  oblongata  in  its  upper  half  is  composed  of  parts  from  the  median 
fissure  backward:  the  anterior  pyramid  overlying  the  fundamental  root  zone,  the  olivary 
body,  anterior  root  zone,  and  the  restiform  body,  composed  of  the  arciform  fibres 
of  the  anterior  pyramid,  the  direct  cerebellar  tract,  and  the  posterior  root  zone.  The 
restiform  body  contains  the  restiform  ganglion  at  its  lower  extremity.  Burdach's  column, 
the  posterior  pyramid  and  clavate  nucleus,  are  behind,  and  are  not  seen  in  the  figure  (see 
figure  8).  The  lower  part  of  the  medulla  contains  the  same  parts  except  the  olive.  The 
decussation  of  the  anterior  pyramids  are  in  front,  about  midway  from  the  pons  and  the 
lower  end  of  the  figure.  The  lower  extremity  of  the  decussation  marks  the  limit  of  the 
medulla  oblongata,  below  which  is  the  spinal  cord,  the  columns  of  which  can  be  read 
upon  the  figure. 


Figure  9. 


92  ARCHITECTURE    OF    THE    BRAIN. 

Figure  10.  Dissection  of  the  pons  and  basal  region  of  the  cerebrum,  viewed  from 
behind.  The  parts  upon  the  right  half  of  the  figure  are  retained  in  order  to  show  the 
relations  of  the  parts  uncovered  by  the  dissection  upon  the  left  side.  In  the  median  line 
in  front  is  a  section  of  the  genu  of  the  corpus  callosum  and  septum  lucidum,  the  anterior 
pillars  of  the  fornix,  the  third  ventricle,  the  fasciculi  teretes  and  posterior  median  fissure 
of  the  iter  and  fourth  ventricle,  the  calamus  scriptorius,  clavate  nuclei,  and  the  posterior 
median  fissure  nf  the  medulla  oblongata  and  spinal  cord.  The  calamus  scriptorius  (pen) 
is  situated  between  the  restiform  bodies,  and  its  point  is  between  the  clavate  nuclei,  at 
the  conjunction  of  the  posterior  median  fissure  of  the  medulla,  and  that  of  the  floor  of 
the  fourth  ventricle  with  the  upper  extremity  of  the  central  canal  of  the  spinal  cord 
(compare  with  Fig.  26,  at  R). 

Upon  the  right  side  of  the  figure,  the  parts  seen  from  before  backward  are:  a  portion 
of  the  corpus  callosum  and  the  internal  capsule,  the  anterior  horn  of  the  lateral  ventri- 
cle, caudate  nucleus,  tsenia  semicircularis,  the  thalamus  opticus  and  anterior 
pillar  of  the  pineal  gland,  the  pison,  posterior  commissure,  pineal  body,  corpora  quadri- 
gemina  and  brachia,  the  processus,  valve  of  Vieussens,  and  corpus  dentatum.  Beneath 
are:  the  fourth  ventricle  at  its  widest  part,  the  arch  of  the  restiform  body,  the 
restiform  triangle,  through  which  the  roots  of  the  seventh  nerve  and  the  anterior  root  of 
the  eigth  nerve  emerge  into  the  fourth  ventricle,  the  former  crossing  the  floor  of  the 
ventricle  to  enter  the  raphe,  and  the  latter  to  join  a  tract,  internal  to  the  restiform  body, 
which  passes  from  the  auditory  nucleus  of  the  medulla  to  the  fillet.  The  tract  just  men- 
tioned forms  the  posterior  layer  of  the  fillet  (see  figure  13,  designation  4i,  and  divides 
the  restiform  triangle  into  two  portions,  an  anterior  part,  which  transmits  the  roots  of 
the  seventh  and  eighth  nerves,  and  an  inferior  part,  through  which  the  fifth  nerve  passes 
in  front  of  the  fasciculi  teretes.  Beneath  the  arch  of  the  restiform  body  is  the  posterior 
root  of  the  eighth  nerve,  which  crosses  the  floor  of  the  fourth  ventricle  to  reach  the  raphe. 
This  root  of  the  eighth  and  that  of  the  seventh  are  the  striae  transversse  on  the  floor  of 
the  ventricle.  At  the  lower  extremity  of  the  restiform  body  is  the  restiform  nucleus  (see 
section  of  restiform  nucleus,  figure  86).  The  clavate  nucleus  is  internal  and  below  the 
restiform  nucleus  and  is  superficial,  while  the  latter  is  imbedded  beneath  a  layer  of  white 
fibres.  The  posterior  pyramid  of  the  medulla,  Gall's  column,  terminates  above  in  the 
clavate  nucleus,  and  the  posterior  root  zone,  column  of  Burdach,  in  the  restiform  nucleus. 

On  the  left  side,  from  before  backward  are:  portions  of  the  caudate  nucleus  and  thal- 
amm,  anterior  fibres  which  pass  forward  to  the  internal  capsule  in  conjunction  with 
the  fillet  of  the  pons  Varolii,  and  are  distributed  to  tbe  anterior  lobe  of  the  cerebrum. 
The  red  nucleus,  or  snbthalmic  ganglion  is  exposed,  and  is  seen  in  relation  with  the  fas 
ciculi  teretes  and  the  wall  of  the  third  ventricle  internally,  and  with  the  fillet  externally. 
The  red  nucleus  gives  off  fibres  to  the  thalamus  and  in  front  to  the  fillet,  and  behind,  a  large 
cord  continuous  with  the  opposite  processus,  which  decussates  with  the  processus 
of  the  same  side  beneath  the  fasciculi  teretes,  under  the  floor  of  the  iter.  External  to 
the  red  nucleus,  the  processus  and  its  decussation,  are  successively  from  within  outward: 
the  fillet,  locus  niger,  and  the  crusta  above;  and  the  fundamental  root  zone  and  pons 
Varolii  below.  Below  the  crusta  are  the  uppermost  fibres  of  the  pons  Varolii,  which  form 
a  tract  derived  from  the  floor  of  the  fourth  ventricle,  that  entering  the  raphe,  passes  for- 
ward to  the  posterior  perforated  space,  and  winding  around  the  front  of  the  crus  cerebri, 
is  directed  backward  to  the  restiform  body,  with  which  it  enters  the  cerebellum.  Below 
the  posterior  extremity  of  this  tract,  is  seen  the  divided  extremity  of  the  restiform  body 
enclosed  by  the  roots  of  the  eighth  nerve,  the  seventh  nerve  passes  through  the  resti- 
form triangle  in  company  with  the  anterior  root  of  the  eighth,  to  enter  the  fourth  ventri- 
cle. Above  the  restiform  body,  the  parts  from  within  outward  are:  the  fasciculi  teretes 
and  floor  of  the  fourth  ventricle,  the  four  layers  of  the  fillet,  and  the  deep  and  superficial 
layers  of  the  pons  Varolii.  The  word  fillet  is  written  upon  the  fundamental  root  zone  (see 
figure  11).  The  fifth  nerve  is  seen  passing  under  the  floor  of  the  ventricle  between  the 
deep  layer  of  the  fillet  and  the  anterior  root  zone.  The  parts  forming  the  posterior  and 
lateial  surfaces  of  the  medulla  can  be  read  upon  the  figure. 


Figure  10. 


94  AEOHITECTUEE    OF   ThJ   BRAIN. 

Figure  11 — Is  a  dissection  in  which  the  right  pyramid  of  the  medulla, 
the  right  half  of  the  pons,  and  the  lower  portion  ot  the  crusta  are  removed, 
exposing  the  continuity  of  the  fundamental  root  zon^,  from  the  spinal  cord 
to  its  termination  in  the  testes  and  brachium  posti.  rius.  In  the  cord, 
it  is  seen  to  lie  external  to  the  direct  pyramidal  tract  (column  of  Turck);  in 
the  medulla  as  far  above  as  the  olive,  it  is  superficial  ind  external  to  the 
anterior  pyramid.  Opposite  the  olive,  it  is  compresset  into  a  prismatic 
shape  (figure  36)  between  this  body  and  the  raphe.  Upoi  the  anterior  sur- 
face of  the  fillet  and  processus,  it  is  a  flat  band  of  fibres  terminating 
above  and  behind  in  the  testes  and  brachium  posterius.  T'lis  tract  is  prob- 
ably a  part  of  the  visual  reflex  system,  by  which  a  pers>  n  affected  with 
ataxia  is  able  to  maintain  the  upright  position  while  the  eyes  are  open. 

The  lower  extremity  of  the  figure  shows  the  superficif  1  tracts  which 
form  the  anterior  and  lateral  columns  of  the  cord,  viz. :  the  cclumn  of  Tiirck 
and  the  fundamental  root  zone  of  the  anterior  column;  and  tl  e  anterior  root 
zone  and  direct  cerebellar  tract,  of  the  lateral  column  of  the  cord.  In  the 
middle  of  the  medulla  is  the  decussation  of  the  pyramids  and  a  flattening 
of  the  fundamental  zone  for  its  accommodation.  The  upper  part  of  the 
medulla  is  seen  to  be  connected  with  the  pons  and  the  cen  bellum  by:  (1) 
the  anterior  pyramid  with  the  reticulated  layer;  (2)  the  fuodamental  root 
zone,  olivary  fasciculus,  anterior  root  zone,  and  fasciculus  from  the  fourth, 
ventricle  forms  the  lemniscus  or  fillet;  (3)  the  grey  matter  of  the  cord 
forms  the  fasciculi  teretes  (not  seen);  (4)  the  restiform  body  connects  the 
posterior  part  of  the  medulla  with  the  cerebellum. 

The  restiform  triangle  is  enclosed,  by  the  edge  of  the  fiFet  in  front,  the 
restiform  body  behind,  and  the  processus  above.  The  parts  transmitted  by 
the  triangle  are  seen  in  figures  9  and  10.  Above  the  pons  are  from  before 
backward:  the  optic  nerves,  commissure  and  tracts,  interpeduncular  space, 
crusta,  locus  niger,  geniculate  bodies,  brachia  and  corpora  quadrigemina. 
Above  the  optic  commissure  is  the  lamina  cinerea. 


^">ind 


Figure  1) . 


96  ARCHITECTURE    OF    THE    BRAIN. 


Figure  12 — may  conveniently  be  observed  in  four  divisions. 
The  upper  portion,  above  the  optic  tract,  shows  the  three 
divisions  of  the  lenticular  nucleus,  surrounded  by  the  internal 
capsule,  upon  which  is  marked  its  divisions,  into  fillet,  motor, 
and  sensory  portions.  The  anterior  part  is  connected  with 
the  optic  commissure  by  the  lamina  cinerea.  The  second 
portion  of  the  figure  is  between  the  lower  arm  of  the  internal 
capsule  and  the  upper  border  of  the  pons;  containing  the 
optic  nerves,  commissure,  tracts,  and  the  corpora  geniculata, 
the  tuber  ciuereum  and  iufundibulum,  corpora  albicantia,  pos- 
terior perforated  space,  crusta,  locus  niger,  upper  extremity 
of  the  fundamental  root  zone,  brachia,  corpora  quadrigemia, 
and  pineal  body.  The  third  portion  contains:  in  front,  a  sec- 
tion of  the  transverse  fibres  and  reticulated  part  of  the  pons,  and 
a  part  of  the  raphe;  further  back,  the  fillet  proper,  consisting  of 
the  olivary  fasciculus,  (which  is  fully  exposed  by  the  removal 
of  the  fasciculus  of  the  fundamental  root  zone),  the  anterior 
root  zone  and  a  fasciculus  from  the  inner  side  of  the  restiform 
body,  derived  from  the  floor  of  the  fourth  ventricle.  Upon 
the  external  margin  of  the  fillet  is  the  restiform  triangle,  con- 
tained behind  by  the  restiform  body  and  the  processus,  which 
terminate  in  the  corpus  dentatum  of  the  cerebellum.  Above 
and  below  the  fillet,  are  seen  the  divided  ends  of  the  funda- 
mental root  zone.  The  lower  portion  of  the  figure  shows  the 
parts  which  form  the  medulla  oblongata,  the  decussation  of 
its  anterior  pyramids,  and  a  section  of  the  spinal  cord. 


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Figure  12. 


98  ARCHITECTURE    OF   THE   BRATN. 


Figure  13.  In  this  figure,  the  right  pyramid  of  the  me- 
dulla, and  the  right  half  of  the  pons,  and  crusta,  have 
been  removed.  Sections  of  the  four  layers  of  the  fillet 
have  also  been  removed.  The  lower  ends  are  marked: 
(1)  tlie  fundamental  root  zone;  (2)  olivary  fasciculus;  (3) 
the  anterior  root  zone,  or  lateral  tract  of  the  medulla; 
(4)  layer  from  the  floor  of  the  fourth  ventricle,  beneath 
which  is  seen  the  anterior  surface  of  the  fasciculi  teretes. 
Internal  to  these  layers  is  the  raphe,  and  a  section  of  the 
pons,  consisting  of  a  reticulated  and  a  commissural  layer. 
External  to  the  fillet  is  the  restiform  triangle,  restiform 
body,  and  processus;  (5)  the  fifth  nerve.  The  processus 
arises  behind  from  the  corpus  dentatum,  is  directed  upward 
beneath  the  fundamental  root  zone  and  the  fillet,  and  inward 
in  front  of,  or  under  the  fasciculi  teretes,  to  decussate  with  the 
opposite  processus  in  the  raphe  of  the  crus  cerebri,  (see  PT, 
figure  26).  Above  the  decussation,  the  fibres  of  the  opposite 
processus  are  seen  to  terminate  in  the  red  nucleus,  which  is  un- 
covered in  the  figure  by  the  removal  of  a  section  of  the  fillet. 
Above  the  red  nucleus  the  fillet  is  seen  to  pass  upward  and 
forward,  beneath  the  fibres  of  the  internal  capsule  derived 
from  the  crusta,  to  join  the  anterior  portion  of  the  capsule. 
The  anterior  commissure  of  the  third  ventricle,  in  its  passage 
outward  to  the  temporal  lobe,  pierces  the  anterior  border  of 
the  fillet.  The  three  divisions  of  the  internal  capsule  are 
indicated  upon  the  figure. 


■■by         ^- 


Figure  13. 


100  ARCHITECTURE   OF   THE   BRAIN. 


Figure  14  illustrates  from  above  downward:  the  inner 
layer  of  the  internal  capsule;  the  lining  membrane  of  the 
lateral  ventricle  which  forms  the  bed  of  the  caudate  nucleus; 
the  thalamus  opticus,  composed  of  concentric  layers  of 
fibrous  matter  between  which  vesicular  layers  are  inter- 
posed; the  divided  extremity  of  the  anterior  commissure 
of  the  third  ventiicle;  the  lamina  cinerea,  optic  tract,  and  the 
parts  in  the  interpeduncular  space;  the  red  nucleus,  from 
which  a  tract  passes  forward  to  the  fillet;  behind  the  red 
nucleus  are  the  corpora  quadrigemina,  from  which  the  brachia 
pass  outward  and  upward  beneath  the  geniculate  bodies  to  the 
internal  capsule;  below  the  red  nucleus  is  the  decussation  of 
the  processes,  thiough  the  raphe  of  the  crura  cerebri;  the 
processus,  fillet,  and  the  restiform  body  enclose  the  restiform 
triangle,  in  front  of  which  are:  the  root  of  the  fifth  nerve,  the 
deep  portion  of  the  fasciculi  teretes,  the  divided  ends  of  the 
layers  of  the  fillet,  the  raphe  and  pons;  below  the  pons  are 
the  tracts  of  the  upper  portion  of  the  medulla,  except  the 
anterior  pyramid,  which  has  been  removed;  the  lower  extrem- 
ities of  these  tracts  have  also  been  removed,  in  order 
to  expose  the  crossing  of  the  fibres  of  the  opposite  anterior 
pyramid  to  form  the  deep  fibres  of  the  lateral  column  of  the 
cord.  The  fibres  of  the  crossed  pyramidal  tract  are  seen  to 
interrupt  the  anterior  grey  column  in  their  passage  from  the 
pyramid  to  the  opposite  lateral  column  of  the  cord. 


Piniial   Gloried 
Nafes 
Testes 


Re.sf.  thicinq} 


^iJi-p.  Oe 


Figure  14. 


102  AECHITECTUEE    OF    THE    BRAIN. 


Figure  15 — Begianing  from  helow,  shows:  (1)  a  section 
of  the  spinal  cord,  and  of  the  columns  of  grey  and  white 
matter,  commissure,  and  central  canal;  (2)  the  columns  upon 
the  posterior  surface  of  the  medulla,  the  clavate,  and  the 
position  of  the  restiform  nuclei;  (3)  the  fourth  ventricle,  fas- 
ciculi teretes,  calamus  scriptorius,  and  the  parts  which  bound 
the  fourth  ventricle,  viz.:  the  restiform  bodies  and  the  processes; 
(4)  the  dentate  bodies,  and  the  relation  of  the  peduncles  of  the 
cerebellum;  the  superior  peduncle  enters  the  under  surface  of 
the  dentate  body,  the  inferior  arches  upward  and  backward  be- 
tween the  superior  and  middle  peduncles,  and  is  also  connect- 
ed with  the  corpus  dentatum,  while  the  middle  peduncle  is 
external,  and  has  no  connection  with  that  body;  (5)  the  pro- 
cesses, above,  are  seen  to  decussate  beneath  the  fasciculi 
teretes,  each  to  connect  with  the  red  nucleus  of  the  opposite 
side;  (6)  between  the  red  nuclei  are  the  third  ventricle,  and 
middle  commissure.  From  within  outward  on  either  side  are: 
the  third  ventricle  and  the  grey  matter  upon  its  sides,  the  red 
nucleus,  fillet,  locus  niger,  and  crusta.  The  fundamental 
root  zone  is  seen  to  be  in  apposition  with  the  posterior  margin 
of  the  fillet;  its  divided  extremity  has  been  exposed  by  the 
removal  of  the  corpora  quadrigemina.  (7)  The  grey  columns 
of  the  cord  are  spread  out  upon  the  floor  of  the  fourth  ven- 
tricle and  continued  through  the  iter  to  the  third  ventricle  by 
the  fasciculi  teretes. 


Figure  15. 


104  AECHITECTUEE  OF  THE  BRAIN. 


Figure  15i  represents  a  dissection  in  which  the  upper  por- 
tion of  the  cerebellum  has  been  removed  by  separating  the 
sides  of  its  transverse  fissure  and  dividing  the  superficial 
layer  of  the  middle  peduncle.  The  upper  portion  is  torn  off 
from  behind  forwards,  exposing  the  corona  radiata  and  the 
upper  surface  of  the  corpus  dentatum.  The  deep  fibres  of 
the  middle  peduncle  are  seen  to  pass  directly  into  the  corona 
radiata,  to  be  distributed  to  the  hemispherical  ganglion  of  the 
cerebellum.  The  superior  peduncle  passes  beneath  the  corpus 
dentatum  to  enter  its  hilus;  and  the  inferior  peduncle,  or  resti- 
form  body,  springing  up  from  between  the  superior  and  mid- 
dle peduncles,  arches  backward  and  is  distributed  to  the  upper 
surface  of  the  dentate  body.  The  corona  radiata  is  made  up 
of  radiating  fibres  from  the  middle  peduncle,  and  from  the 
corpus  dentatum.  The  corpora  quadrigemina,  and  fasciculi 
teretes  of  the  iter,  have  been  removed  in  order  to  show  the 
decussation  of  the  processes  and  their  connection  with  the  red 
nuclei.  Above  the  decussation  is  the  raphe,  on  either  side  of 
which  is  the  red  nucleus,  fillet,  locus  niger,  and  crusta.  Be- 
hind the  crusta  is  the  vertical  line  of  the  crus  cerebri  and  the 
divided  extremity  of  the  fundamental  root  zone.  Below  the 
decussation  are  the  divided  ends  of  the  fasciculi  teretes  and  the 
iter,  the  valve  of  Yieussens,  and,  lower  down,  between  the 
corpora  dentata,  is  the  white  substance  of  the  middle  lobe 
of  the  cerebellum. 


Figure  15^. 


THE  CEREBEAL  HEMISPHERE. 


Superior  border. 
Figs.  1-16-IV-24. 


External  border. 
Figs.  2-7-16-17- 
24-25. 


Inferioi 
Figs. 


border. 
1-17-26. 


Separated  from  the  remaining  portion  of  the  axis,  the 
cerebral  hemisphere  in  general  view  resembles  the  quarter 
section  of  an  ovoid.  It  is  elongated  from  before  backwards, 
bluntly  pointed  at  each  extremity,  and  presents  for  examination) 
three  borders  which  enclose  three  surfaces.  The  borders  are: 
superior,  external,  and  inferior.  The  superior  border  forms 
the  margin  of  the  great  longitudinal  fissure,  its  convexity  is 
upward,  and  it  extends  from  the  posterior  extremity  of  the 
occipital  lobe  to  the  anterior  angle  of  the  orbital  surface  of  the 
frontal  lobe  of  the  hemisphere,  dividing  the  external  from 
the  internal  surface.  The  external  border  arches  around  the 
anterior  border  of  the  orbital  surface  of  the  frontal  lobe  to  the 
fissure  of  Sylvius,  and  around  the  outer  border  of  the  tem- 
poral and  occipital  lobes  to  the  posterior  extremity  of  the 
hemisphere, where  it  joins  the  superior  border  at  an  angle.  This 
border  is  interrupted  by  a  broad  notch  opposite  the  fissure 
of  Sylvius,  which  receives  the  posterior  arched  border  of  the 
orbital  plate  of  the  frontal  and  sphenoid  bones.  Behind  the 
projection  of  the  temporal  lobe  this  border  is  arched  upward 
over  the  cerebellum.  It  forms  a  notch  in  front  with  the  cere- 
bellum which  lodges  the  petrous  portion  of  the  temporal  bone, 
and  marks  the  position  of  the  external  auditory  meatus. 
This  border  separates  the  external  and  the  inferior  surfaces. 
The  inferior  border  is  internal  along  the  median  line  of  the 
base  of  the  cerebrum  and  is  in  three  portions.  The  anterior 
and  posterior  portions  form  the  margins  respectively  of  the 
anterior  and  posterior  median  fissures.  The  middle  portion 
crosses  the  hilus  of  the  hemispherical  ganglion,  dividing  it  into 

106 


THE    CEREBRAL    HEMISPHERE.  107 

two  unequal  jxirts:  that  below,  assists  in  the  formation  of  the 
hilus  of  the  cerebrum,  and  that  above,  is  called  the  intrafissural 
portion  of  the  hilus,  because  it  is  surrounded  by  the  great 
longitudinal  fissure.  Crossing  this  border  at  the  junction  of 
its  anterior  and  middle  portion  is  a  broad  groove  continuous 
laterally  with  the  anterior  perforated  space,  and  in  front  with 
the  anterior  surface  of  the  corpus  callosum.  This  groove  is 
converted  into  a  foramen  by  the  optic  nerve,  and  lodges  the 
anterior  cerebral  artery.  The  bottom  of  the  groove  is  con- 
vex from  within  outward,  resembling  a  large  cord,  and  is 
named  the  cordon,  because,  in  the  early  development  of  the 
brain  this  part  forms  the  connection  of  the  hemisphere  to  the 
parts  below  it,  and  because,  the  convolutions  of  the  cerebrum 
can  be  traced  as  loops,  which  begin  and  end  in  this  locality. 
The  cordon  is  composed  of  a  large  mass  of  antero-posterior 
fibres  disposed  in  horizontal  laminte. 

The  surfaces  of  the  hemisphere  are:  external,  inferior,  and 
internal.  The  external  surface  is  pointed  before  and  behind, 
and  convex  in  every  direction,  corresponding  to  the  concavity 
of  the  inner  surface  of  the  vault  of  the  cranium,  with  which 
it  lies  in  contact.  Behind  the  center  of  this  surface  is  an 
oval  eminence  corresponding  to  the  parietal  eminence  of  the 
skull,  which  is  situated  vertically  above  the  external  auditory 
meatus.  The  vertex  is  midway  betweeii  the  occiput  and  the 
nasion,  and  is  in  a  direct  line  with  the  parietal  eminence 
and  the  external  auditory  meatus.  The  relations  of  these 
points  to  the  external  surface  of  the  hemisphere  are  of  oreat 
assistance  in  locating  the  lobes  and  fissures  beneath  the  surface 
of  the  head. 

This  surface  of  the  hemisphere  is  marked  by  two  promi- 
nent fissures,  the  fissures  of  Sylvius  and  of  Eolando-    and  bv       """  ''°'"°"^° 

'       '"""-*    "JJ  Figs.  16  34. 

minor  fissures  that  separate  the   convolutions  and  the  lobes 
a7id  are  named  after  the  parts  which  they  divide. 


16  i4-25. 


f  Sylvius 
and 
Figs.  16  34. 


108 


AECHITECTUEE    OF    THE    BRAIN. 


Insula.     Fig.  18. 


of  Sylvius  on 
urface  cf  the 


.n  of  the  fis- 
□  f    Rolando. 


Tlie  fissure  of  Sylvius  begins  at  the  anterior  perforated 
space,  winds  in  front  of,  to  the  outer  side,  and  above  the 
temporal  lobe,  where  it  divides  into  a  short  and  long  arm; 
the  former  projecting  upward  and  forward  into  the  frontal 
lobe,  and  the  latter  is  directed  backward  to  the  middle  of 
the  parietal  eminence.  This  fissure  is  very  deep  and  branched 
at  its  bottom  to  enclose  a  bunch  of  convolutions,  called  the 
insula,  or  island  of  Eiel.  The  insula  is  exposed  by  separat- 
ing the  margins  of  the  fissure  of  Sylvius,  and  the  convolu- 
tions which  cover  it  are  called  the  operculum — a  name  which 
must  not  be  confounded  with  the  aperculum,  or  hilus  of  the 
hemispherical  ganglion.  The  position  of  the  fissure  of  Syl- 
vius is  indicated  upon  the  surface  of  the  head  by  a  line 
drawn  from  the  outer  canthus  of  the  eye  to  the  middle  of  the 
parietal  eminence,  and  if  continued  this  line  would  pass  through 
the  crown  and  the  opposite  external  auditory  meatus. 

The  fissure  of  Rolando  extends  from  the  middle  of  the 
posterior  arm  of  the  fissure  of  Sylvius,  upward  and  slightly 
backward  to  the  vertex,  dividing  the  external  surface  of  the 
hemisphere  into  anterior  and  posterior  parts,  from  which  it 
derives  the  name  of  central  fissure.  Its  situation  is  indicated 
upon  the  surface  of  the  head  as  lying  beneath  the  upper  por- 
tion of  a  line  extending  from  the  inferior  angle  of  the  malar 
bone  to  the  vertex.  The  convolutions  upon  the  external  sur. 
face  of  the  hemisphere  are  represented  upon  figure  16,  and 
are  named:  first,  second  and  third,  in  the  several  regions  of 
the  surface,  viz.:  frontal,  parietal,  occipital,  and  temporal, 
with  the  exception  of  the  central  region,  in  which  there  are 
only  two  convolutions,  the  anterior  and  posterior  central,  one  on 
each  side  of  the  central  fissure  of  Rolando;  and  the  insular 
region  consists  of  five  or  sis  small  convolutions  contin- 
uous with  those  of  the  sides  of  the  fissure  of  Sylvius. 


THE    CEREBRAL    HEMISPHERE. 


109 


Inierior  surface  of 
a  hemisphere. 
Figs.  2  17. 


Orbital  portion. 


Temporo-occipital 
portion. 


The  inferior  surface  of  the  hemisphere,  before  descri?jed 
with  the  under  surface  of  the  cerebrum,  re(_[uires  a  short 
review  in  this  connection.  It  is  divisible  in  three  portions: 
an  anterior  or  orbital  portion,  which  is  triangular,  concave 
from  side  to  side,  and  elevated  upon  its  internal  border, where 
it  is  marked  by  a  longitudinal  fissure  which  lodges  the  olfac- 
tory bulb  and  nerve.  It  is  marked  by  three  indistinct  con- 
volutions: anterior,  external,  and  posterior.  The  temporo- 
occipital  surface  looks  obliquely  inward,  is  concave  from 
before  backward,  and  is  marked  by  several  convolutions,  the 
outermost  of  which  is  the  under  surface  of  the  third  temporal 
convolution,  internal  to  which  in  succession  are:  the  fusiformis, 
lingualis,  and  hippocampal  convolutions.  The  latter  is  con- 
tinuous behind  the  splenium  of  the  corpus  callosum,  with  the 
convolution  of  the  gyrus,  and  in  front  with  the  ungual,  a 
small  convolution  which  is  turned  inward  upon  the  margin  of 
the  hilus  cerebri.  The  remaining  portion  of  this  surface  con- 
sists of  a  crescent  depression  which  includes  the  interpedun- 
cular space  and  the  divided  surface  of  the  crus  cerebri,  around 
the  outer  margin  of  which  is  the  fissure  of  Bichat. 

The  internal  surface  of  the  hemisphere  presents  two  por- 
tions for  examination:  a  convoluted  portion  above,  in  front, 
and  behind;  and  an  enclosed  portion,  presenting  the  divided 
surfaces  of  commissures  and  the  lateral  wall  of  the  third 
ventricle,  which  together  fill  up  the  upper  part  of  the  aper- 
culum  or  hilus  of  the  hemispherical  ganglion,  before  called 
the  iutrafissural  portion  of  the  hilus.  The  convoluted  convoluted  port 
portion  of  the  internal  surface  of  the  hemisphere  encloses  the 
outer  surface  of  the  corpus  callosum,  from  which  it  is  separ- 
ated by  the  fissure  of  the  gyrus  fornicatus,  or  ventricle  of  the 
corpus  callosum.  It  is  wider  behind  than  in  front,  and  shaped 
like  the  falciform  process  of  the  dura  mater,  against  which  it 
lies;  its  posterior  border,  which  is  the  margin  of  the  posterior 


110 


ARCHITECTURE    OF   THE    BRAIN. 


Intrafissural  regi( 
of  the  internal 
surface    of    the 


median  fissure,  rests  upon  the  tentorium  cerebelli.  This  por- 
tion of  the  internal  surface  is  marked  by  two  distinct  fissures, 
the  calloso-marginal,  and  parieto-occipital.  The  anterior  fis- 
sure, calloso-marginal,  begins  in  front  beneath  the  genu  of 
the  corpus  callosum,  and,  winding  in  front  and  above  this 
body  is  directed  upward  and  backward  to  terminate  upon  the 
margin  of  the  great  longitudinal  fissure  behind  the  vertex  and 
the  upper  extremity  of  the  central  fissure  of  Rolando.  The 
calloso-marginal  fissure  is  separated  from  the  corpus  callosum 
by  the  convolution  of  the  gyrus  fornicatus.  The  parieto- 
occipital fissure  begins  below  the  hippocampal  convolution 
upon  the  inferior  surface  of  the  hemisphere,  extends  upward 
and  backward,  across  the  internal  border  and  internal  surface, 
to  a  point  upon  the  margin  of  the  longitudinal  fissure  which 
lies  beneath  the  crown  of  the  head.  Above  the  inferior  or 
internal  border  of  the  hemisphere  it  gives  off  a  branch  fissure, 
the  calcarine,  which  passes  backward  to  the  posterior  extrem- 
ity of  the  occipital  lobe.  These  divisions  of  the  parieto-oc- 
cipital fissure  inclose  a  wedge  shaped  bunch  of  convolutions, 
called  the  cuneus,  which  is  the  center  of  sight  memories. 
The  convolutions  seen  upon  this  surface  from  behind  for- 
ward are:  the  inner  margin  of  the  lingualis,  the  cuneus,  quad- 
ratus,  paracentral,  marginal  and  gyrus  fornicatus. 

The  intrafissural  portion  of  the  internal  surface  of 
the  hemisphere  is  bounded  in  front  by  the  rounded  surface  of 
the  cordon,  and  from  below  backward,  the  ungual  and  hippo- 
campal convolutions  which  are  continued  above  and  in  front 
of  the  corpus  callosum  by  the  gyrus  fornicatus,  which  ter- 
minates at  the  cordon  in  front.  The  surface  included  within 
these  boundries  is  filled  up  by  sections  of  the  corpus  callosum, 
fornix,  septum  lucidum,  anterior,  middle  and  posterior  com- 
missures of  the  third  ventricle,  lamina  cinerea,  optic  commis- 
sure,  tuber  cinereum   and   infudibulum,    corpora   albicantia, 


THE    CEREBRAL    HEMISPHERE. 


Ill 


raphe  of  the  crua  cerebri,  the  decussation  of  the  processes,  the 
iter,  corpora  quadrigemina,  and  pineal  body.  It  contains  the 
outer  wall  of  the  third  ventricle,  formed  by  the  inner  surface 
of  the  thalamus  opticus;  and,  extending  from  the  splenium, 
beneath  the  corpus  callosum  and  fornix,  to  the  anterior  pillars 
of  the  fornix  in  front,  is  the  fissure  of  Bichat,  the  anterior 
extremity  of  which  is  the  foramen  of  Monro. 

If  the  above  parts  are  removed,  and  also  the  crus 
cerebri,  there  is  seen  a  large  oval  opening,  leading  into  the 
center  of  the  hemisphere,  which  is  the  aperculum,  or  hilus  of 
the  hemispherical  ganglion.  The  grey  matter  of  the  gan- 
glion terminates  at  the  margin  of  the  aperculum,  and  is 
plainly  seen  at  its  lower  part,  where  it  is  called  the  fascia 
dentata.  Internal  to  its  upper  margin  is  a  tract  of  longi- 
tudinal fibres,  called  the  superior  longitudinal,  or  commissure 
of  the  gyrus.  The  cordon  is  seen  to  be  composed  of  hori- 
zontal layers  of  longitudinal  fibres,  and  about  half  an  inch 
above  its  lower  surface  is  a  groove,  seen  in  figure  17,  which 
is  the  bed  of  the  anterior  commissure  of  the  third  ventricle. 
Attached  to  the  apex  of  the  ungual  convolution  are  the 
lower  extremities  of  the  corpus  fimbriatum  and  the  ta3nia 
semicircularis,  between  which  is  seen  the  lower  extremity  of 
the  fissure  of  Bichat  leading  to  the  middle  cornu  of  the  lat- 
eral ventricle. 

The  convolutions  of  the  hemisphere  which  compose  the 
hemispherical  ganglion  can  be  recollected  in  the  following 
order:  external,  internal,  and  posterior  orbital;  insula;  first, 
second,  and  third  f  I'ontal;  anterior,  and  posterior  central;  first, 
second,  and  third  parietal;  first,  second,  and  third  occipital; 
first,  second,  and  third  temporal;  fusiformis;  lingualis;  ungual, 
hippocampal,  and  gyrus  fornicatus;  cuneus,  quadratus,  para- 
central and  marginal. 


Ape 


Lower  extremities 
of  the  corpus  fim- 
briatum, taenia 


ganglia 


112  ARCHITECTURE  OF  THE  BRAIN. 

Figure  16  is  a  representation  of  tlie  external  surface  of  a 
hemisphere  and  the  convolutions  and  fissures  upon  it.  The 
principal  fissures  are:  (1)  the  fissure  of  Sylvius,  com- 
mencing below  at  the  junction  of  the  anterior  and  middle  third 
of  the  lower  border,  and  extending  upward  and  backward,  ter. 
minates  in  the  middle  of  the  parietal  eminence,  and  a  short 
anterior  arm  is  directed  upward  and  forward  into  the  frontal 
lobe;  and  (2)  the  fissure  of  Rolando,  commencing  below  about 
the  middle  of  the  posterior  arm  of  the  fissure  of  Sylvius, 
extends  upward  and  backward  to  the  vertex,  dividing 
the  upper  portion  of  the  of  the  hemisphere  into  anterior 
and  posterior  halves,  hence  this  fissure  is  often  called  the 
central  fissure.  The  convolutions  upon  tliis  surface  are: 
orbital,  frontal,  central,  parietal,  occipital  and  temporal. 
The  orbital  convolutions  are:  external,  posterior  and  in- 
ternal— seen  in  figurq  2.  The  first  frontal  convolution 
forms  the  outer  surface  of  the  marginal,  convolution  (figure 
17),  joins  the  orbital  below,  and  the  upper  extremity  of  the 
anterior  central  above.  The  second  frontal  has  two  portions; 
the  upper  portion  joins  the  middle  part  of  the  anterior  central, 
and  the  lower  portion  joins  the  posterior  part  of  the  third 
frontal.  The  third  frontal  surrounds  the  anterior  arm  of  the 
fissure  of  Sylvius.  The  anterior  central  convolution  is  con- 
tinuous with  the  marginal  above  and  tlie  insula  below.  It 
will  be  seen  that  these  convolutions  form  arches,  which 
through  the  orbital  and  and  insular  convolutions  are  connected 
with  the  cordon  (figure  17).  The  posterior  central  is  con- 
nected with  the  insula  below,  dna  the  quadratus  above,  and 
behind  with  the  parietal  lobes.  This  system  includes  the 
first  temporal,  parietal  convolutions,  posterior  central,  quad- 
ratus, gyrus  and  hippocampal  convolutions,  completing  arches 
from  the  cordon  in  front.  Of  the  remaining  convolutions, 
they  are  seen  to  join  the  lower  temporal  and  hippocampal 
convolution  at  angles,  and  are  continued  by  them  to  the  cor- 
don. It  will  be  observed  that  this  arrangement  of  the  con- 
volutions of  the  hemisphere  is  admirably  adapted  to  the 
passage  of  longitudinal  fibres  from  every  part  of  the  surface 
of  the  brain  to  the  frontal  lobes,  which  are  the  seat  of  the 
intellect  and  judgment. 


Fiuuro  1(5. 


114  ARCHITECTURE    OF    THE    BRAIN. 

Figure  17  shows  the  internal  surface  of  the  hemispherical 
ganglion  and  the  convolutions  of  which  it  is  composed.  Its 
interior  is  exposed  by  the  removal  of  the  corpus  callosum, 
fornix,  septum  lucidum,  basal  ganglia,  and  the  crus  cerebri; 
parts  of  which  fill  up  the  hilus  or  aperculum  of  the  gan- 
glion. There  are  two  principal  fissures  upon  this  surface: 
(1)  the  callosomarginal,  beginning  at  the  cordon  below,  and, 
arching  above  the  gyrus  fornicatus,  terminates  upon  the 
margin  of  the  great  longitudinal  fissure  between  the  para- 
central lobule  and  the  quadratus,  a  little  behind  the  upper 
extremity  of  the  fissure  of  Rolando;  (2)  the  parieto-occipital 
fissure  commences  upon  the  lower  surface  of  the  hemisphere 
external  to  the  hippocampal  cc>n volution,  and  passing  upward 
and  backward  above  the  internal  margin  of  the  hemisphere 
divides  into  two  arms  which  enclose  the  cuneus.  The  an- 
terior arm  terminates  in  the  margin  of  the  longitudinal  fissure 
at  a  point  beneath  the  superior  angle  of  the  occipital  bone, 
the  crown;  the  posterior  arm  passes  backward  to  the  extrem- 
ity of  the  occipital  lobe,  and  is  called  the  calcarine  fissure. 
The  convolutions  and  their  boundaries  can  be  seen  upon  the 
figure,  and  also  the  connections  by  which  they  are  continued 
to  the  cordon.  The  grey  matter  of  the  hemisphere  terminates 
within  the  margin  of  the  aperculum,  and,  being  distinctly  seen 
below  is  called  the  fascia  dentata.  Within  the  upper 
margin  of  the  aperculum  is  a  large  tract  of  longitudinal 
fibres,  extending  from  the  cordon  to  the  hippocampal  convo- 
lution, which  is  the  superior  longitudinal,  or  commissure  of 
the  gyrus.  The  cordon  is  a  large  collection  of  longitudinal 
fibres,  disposed  in  horizontal  layers,  underlying  the  anterior 
portion  of  the  internal  capsule  and  basal  ganglia.  Its  under 
surface  is  rounded  and  exposed  on  the  base  of  the  brain  at 
the  anterior  perforated  space.  It  is  perforated  by  large  ves- 
sels which  supply  the  basal  ganglia.  The  anterior  commis- 
sure of  the  third  ventricle  passes  through  it  in  a  lateral  direc- 
tion, and  its  bed,  uncovered,  is  seen  in  the  figure.  The 
ungual  convolution  is  seen  turning  backward  behind  the  cor- 
don, and,  attached  to  its  apex  are  the  ttenia  semicircularis  and 
corpus  fimbriatum,  between  which  is  the  lower  extremity  of 
the  fissure  of  Bichat  entering  the  middle  cornu  of  the  lateral 
ventricle  from  the  under  surface  of  the  brain.  The  parts 
which  fill  up  the  aperculum  are  seen  in  figure  26.  The  upper 
part  of  the  aperculum  is  interhemispherical;  the  lower  por- 
tion transmits  the  eras  cerebri,  and  is  part  of  the  hilus  of  the 
cerebrum. 


Figure  17. 


116  ABCHITECTURE  OF  THE  BHAIN. 


Figure  18.  The  insula  is  exposed  by  the  removal  of  the 
convolutions  forming  the  margins  of  the  fissure  of  Sylvius. 
The  convolutions  removed  are  called  its  operculum  (cover),  and 
must  not  be  confounded  with  the  aperculum  or  hilus  of  the 
hemispherical  ganglion  (figure  17). 

The  insula,  or  island  of  Kiel,  is  composed  of  six  or  seven 
small  convolutions,  which  are  continuous  above  and  below 
with  those  of  the  margins  of  the  Assure  of  Sylvius.  The 
anterior  extremities  of  the  convolutions  forming  the 
insula  are  all  directed  toward  the  cordon,  which  is  at  the  bot- 
tom of  the  fissure  of  Sylvius  and  occupies  the  anterior  per- 
forated space  (figure  17).  Above  ihe  insula  is  an  arch,  called 
the  vault,  composed  of  superimposed  horizontal  layers  of 
fibres,  derived  from  the  corpus  callosum  and  the  internal  cap- 
sule. This  disposition  of  the  fibres,  derived  from  these 
bodies,  permits  the  passage  of  longitudinal  fibres  between 
them  in  their  passage  outward  to  the  convolutions  of  the  sur- 
face. The  same  arrangement  of  fibres  from  these  bodies  is 
seen  below  the  insula,  between  which  the  fibres  of  the  exter- 
nal longitudinal  commissure  are  interposed  in  their  passage 
from  the  posterior  to  the  anterior  lobes  of  the  hemisphere. 
Behind  the  insula  are  fibres  from  the  thalamus  passing  back- 
ward between  the  plates  or  layers  of  the  internal  capsule. 
The  internal  capsule  encloses  the  insula,  which  is  the  outer- 
most part  that  fills  up  the  funnel  shaped  concavity  enclosed 
by  the  capsule.  Beneath  the  convolutions  of  the  hemis- 
phere is  the  internuncial  layer  of  short  fibres,  which  extend 
between  adjacent  convolutions. 


Figure  18. 


118  AECHITECTURE  OF  THE  BRAIN. 


Figure  19.  Upon  the  removal  of  the  insula  and  the  sub- 
convolutional  white  layer  which  subtends  its  grey  substance, 
a  broad  and  thin  layer  of  grey  matter  is  uncovered,  called  the 
claustrum,  which  is  difficult  to  represent  in  a  lateral  dissec- 
tion, but  is  to  be  seen  in  a  vertical  section,  (see  vertical  sec- 
tions from  figures  10  to  18).  This  layer  of  grey  matter  ia 
thicker  below  than  above,  and  covers  the  external  surface  of  the 
external  capsule,  with  which  it  is  in  immediate  relation.  This 
layer  having  been  removed,  the  dissection  here  represented 
shows  the  external  capsule  to  be  composed  of  fibres  radiating 
upward  from  beneath  the  external  longitudinal  commissure. 
This  layer  of  fibres  is  very  thin  immediately  above  the  com- 
missure and  thick  beneath  the  vault.  Its  fibres  are  derived 
from  the  outer  surface  of  the  lenticular  nucleus,  and  pass 
upward  to  unite  with  the  under  surface  of  the  fibres  of  the 
vault,  into  which  they  are  lost.  The  external  longitudinal 
commissure  is  distinctly  seen  to  form  a  part  of  the  cordon  and 
to  enter  the  anterior  part  of  the  internal  capsule  in  front  of  the 
lenticular  body.  Its  posterior  extremity  intermingles  with  the 
posterior  fibres  of  the  corpus  callosum  and  internal  capsule, 
and  with  them  is  distributed  to  the  posterior  convolutions  of 
the  hemisphere. 


Figure  19. 


120  AKCPIITECTDEE    OF   THE   BRAHST. 


Figure  20.  In  this  dissection  the  outer  fibres  of  the 
external  capsule  are  removed  to  expose  the  external  division  of 
the  lenticular  body  (putamen).  A  small  fragment  of  the 
external  capsule  is  seen  above  the  external  longitudinal  com- 
missure, and  the  deeper  portion  of  it  is  seen  above  the  ex- 
posed portion  of  the  lenticular  nucleus.  These  latter  fibres 
pass  directly  upward  from  the  surface  of  the  nucleus  to  enter 
the  vault. 

In  front  of  the  lenticular  body,  the  external  longitudinal 
commissure  joins  with  the  anterior  portion  of  the  internal 
capsule;  and  behind,  its  fibres  interlace  with  the  posterior  and 
inferior  radiation  of  the  capsule.  Between  the  posterior  part 
of  the  lenticular  nucleus  and  the  genu  of  the  internal  capsule, 
the  posterior  fibres  from  the  thalamus  emerge  to  pass  back- 
wards to  the  occipital  lobes.  These  fibres  from  the  thalamus 
contain  the  optic  radiation  to  the  cuneus  and  the  posterior 
convolutions  of  the  hemisphere.  The  radiation  of  the  fibres 
derived  from  the  internal  capsule  and  corpus  callosum,  form- 
ing the  vault,  surrounds  the  lenticular  nucleus,  except  a  space 
opposite  to  the  fissure  of  Sylvius,  which  is  occupied  by  the 
longitudinal  commissure  and  cordon. 


Figure  20. 


122  AKCHITECTDRE    OF    THE    BRAIN. 


Figure  21.  The  lenticular  nucleus  and  upper  portion  of 
the  crusta  fibres  of  the  internal  capsule  have  been  removed, 
exposing  the  anterior  and  posterior  distribution  of  fibres  from 
the  thalamus.  The  fillet  is  seen  to  emerge  from  internal  to 
the  crusta,  and  to  pass  forward  to  join  the  anterior  distribu- 
tion of  fibres  from  the  tlialamus.  The  external  longitudinal 
commissure  is  fully  exposed,  and  is  seen  to  unite  with  the  fillet 
fibres  in  front  after  forming  the  mass  of  fibres  which  consti- 
tute the  cordon.  The  anterior  commissure  of  the  third  ven- 
tricle passes  obliquely  outward  and  backward,  across  the  de- 
pression which  lodges  the  lenticular  body,  to  reach  the  outer 
extremity  of  the  inferior  ramus,  or  temporal  distribution,  of 
the  internal  capsule. 


Figure  21. 


124  ARCHITBCTUKE    OF    THE    BRAIN. 


Figure  22.  The  external  longitudinal  commissure  has 
been  removed.  The  anterior  commissure  of  the  third  ven- 
tricle is  fully  exposed.  Behind  it  are  the  divided  ends  of  the 
crusta  and  the  fillet.  Above  is  seen  a  portion  of  the  external 
surface  of  the  caudate  nucleus,  from  which  the  internal  cap- 
sule has  been  removed.  The  thalamus  consists  of  concentric 
laminae,  between  which  are  layers  of  grey  matter.  At  the 
bottom  of  the  cavity,  made  by  washing  out  the  grey  matter 
of  the  thalamus,  is  seen  the  red  nucleus  of  the  tegmentum. 
The  fibres  of  the  corpus  callosum  are  distinctly  seen  to  decus- 
sate with  those  of  the  internal  capsule.  The  laminae  of 
which  each  is  composed  overlie  each  other,  and  break  off  in 
pointed  plates,  as  seen  in  the  posterior  part  of  the  figure. 


Figure  22. 


126  AROHITECTUKE    OF    THE    BRAIN. 


Figure  23 — Is  an  intrahemispherical  view  of  the  internal 
surface  of  a  hemisphere,  in  which  the  fissures  are  seen  as  pro- 
jections upon  the  surface,  and  the  convolutions  as  depressions. 
The  internal  capsular  fibres  are  entirely  removed,  and  the 
laminae  of  the  corpus  callosum  are  seen  projecting  from  the 
surface.  Above  the  corpus  callosum  are  the  longitudinal 
fibres  of  the  gyrus  fornicatus,  called  the  superior  longitudinal 
commissure,  which  is  seen  from  above  in  figure  3.  Beneath 
the  corpus  callosum  is  a  portion  of  the  lining  membrane  of 
the  lateral  ventricle  which  covers  the  ventricular  surface  of 
the  caudate  nucleus.  The  ventricle  is  opened  behind  the 
thalamus,  exposing  a  portion  of  the  fornix  and  the  hippo- 
campi. The  concentric  layers  which  compose  the  thalamus 
are  well  seen  in  the  figure,  as  well  as  the  relative  positions  of 
this  body,  the  fillet,  crusta  and  the  anterior  commissure  of 
the  third  ventricle. 


Figure  23. 


CEREBRAL  LOCALIZATION. 


The  observation  of  the  results  of  disease  and  accidents 
in  man,  and  the  experiments  of  Ferrier,  Horsley  and  others, 
upon  the  brains  of  the  lower  animals,  have  established  the 
fact,  that  certain  parts  (>f  the  hemispherical  ganglion  are  en- 
dowed with  special  functions.  The  areas  that  receive  the 
impressions  from  certain  sensory  nerves,  and  that  control  the 
movements  of  certain  parts  of  the  body,  are  definitely 
mapped  upon  the  surface  of  the  brain,  and  experience  has 
demonstrated  that  these  discoveries  are  worthy  of  confidence. 

It  is  not  to  be  supposed,  however,  that  a  science  which 
is  so  recent  in  its  origin  has  reached  a  stage  of  perfection 
which  is  absolutely  reliable,  but  sufficient  is  already  proven 
to  wan-ant  the  belief  that  more  definite  knowledge  is  at  hand. 

It  has  long  been  known  that  injuries  and  inflammation 
involving  the  central  part  of  the  surface  of  the  brain  are 
productive  of  convulsions;  that  an  injury  to  the  third  frontal 
convolution  of  the  left  side,  (Broca's  convolution,)  destroys 
the  ability  to  speak;  that  disturbances  of  the  intellect  occur 
in  afi^ections  of  the  anterior  lobes  of  the  brain;  and  that 
memory  suffers  from  disease  of  the  occipital  lobes.  These 
general  observations  are  confirmed  by  more  recent  and 
careful  investigation.  The  areas  devoted  to  the  general 
functions  of  the  mind,  viz.:  judgment,  memory,  and  motion, 
are  now  more  definitely  described,  and  subdivided  into  parts 
Motor  area  of  the  to  whlch  speclfic  functious  arc  attributed.  The  motor  area 
is  situated  about  the  fissure  of  Rolando,  viz. :  in  the  posterior 
portion  of  the  frontal  convolutions,  the  anterior  and  posterior 
central  convolutions,  and  in  the  superior  parietal  lobule. 
This  area  is  divided  into  smaller  portions,  which  are  asso- 
ciated with  certain  muscular  movements,  as  indicated  upon  Fig. 


brain. 


CEREBRAL    LOCALIZATION.  129 

24.  Common  sensation  and  muscular  sense  are  situated  above 
and  behind  the  posterior  extremity  of  the  fissures  of  Sylvius; 
hearing  and  the  memory  of  words  are  located  in  the  upper 
temporal  convolutions;  smell  and  taste,  in  the  apex  and 
under  surface  of  the  temporal  lobe;  and  vision  and  the  sight 
memory  of  words,  in  the  occipital  lobes  and  the  cuneus. 
For  more  exact  information  the  reader  is  referred  to  the 
works  of  Ferrier  and  Horsley. 

The  above  observations  are  intended  to  direct  the  atten- 
tion to  the  importance  of  the  study  of  the  anatomical  rela- 
tions between  the  surface  of  the  brain  and  the  surface  of  the 
head,  and  also  of  the  deeper  parts  of  the  brain  to  its  ex- 
ternal surface.  This  is  the  more  important,  because  the  walls 
of  the  cavity  which  contain  the  brain  are  rigid,  requiring  ihe 
surgeon  to  direct  his  operations  upon  this  organ  as  near  the 
seat  of  the  lesion  as  possible.  We  have  seen  that  the  struc- 
tures within  the  brain  are  more  or  less  important  for  the 
immediate  support  of  life  and  mental  integrity,  therefore, 
it  is  quite  essential  that  the  surgeon  should  know  the  sit- 
uation and  direction  to  the  parts  lying  beneath  the  point  ex- 
posed by  the  trephine,  and  the  safe  direction  in  which  he 
may  venture  to  puncture  a  ventricle,  open  an  abcess,  or  use 
the  knife  in  the  removal  of  a  tumor.  The  cranial  cavity  is 
a  very  important  surgical  space,  and  the  invader  should  be 
better  acquainted  with  its  anatomy  than  with  that  of  any  other 
region,  on  account  of  the  important  functions  of  its  contents. 
It  is  not  sui'prising,  in  the  present  state'of  our  knowledge  of 
the  anatomical  relations  of  the  parts  of  the  brain,  to  learn 
of  recoveries  after  great  violence  has  been  done  to  this  deli- 
cate organ,  and  at  other  times,  that  death  has  resulted  from 
a  mere  puncture. 

For  certain  reasons,  exact  localization  is  an  impossibility, 
though  practically  this  may  be  obtained  within  approximate 
limits.  The  brain  may  be  exposed,  if  not  in  the  precise 
locality  sought  after,  yet  near  to  the  situation,  which  may  be 
recognized  by  appearance  or  electrical  test.  It  is  of  little 
consequence  that  a  larger  portion  of  the  skull  is  afterward 


Area  of 

CO 

mmon 

s 

land 

■ 

nuscu 

lai 

■  sense. 

He 

taring 

rie 

id  wore 

So 

lellar 

id 

taste, 

Vh 

3iona 

nd 

sight 

130 


ARCHITECTURE    OF    THE    BRAIN. 


System  of  localiz 
tion  presented. 


Prominent  points 
and  lines  upon 
the  skull. 


removed,  in  order  to  reach  the  desired  point.  Experience  in 
the  examination  of  different  skulls  and  heads  is  of  great 
assistance  in  determining  the  situation  of  the  prominent 
fissures  and  convolutions  beneath  the  surface,  enabling  the 
surgeon  to  place  his  finger  over  them  without  effort,  or  the 
assistance  of  instruments.  The  variations  in  different  subjects 
are  due:  first,  to  the  fact  before  mentioned,  that  no  two  brains 
are  identically  marked,  nor  are  the  opposite  sides  of  the 
same  brain  symmetrical;  second,  there  is  frequently  a  dispro- 
portion between  the  cerebrum  and  the  cerebellum;  when 
the  latter  organ  is  large  and  deep  in  its  vertical  diameter, 
it  has  the  effect  of  elevating  the  posterior  part  of  the 
cerebrum  and  the  vertex  of  the  skull,  thereby  deranging 
the  lines  drawn  upon  the  head  as  guides  to  the  parts  beneath; 
third,  what  is  true  of  the  brain  may  also  be  said  of  the  skull, 
that  parts  which  are  prominent  in  some  skulls  are  almost 
wanting  in  others;  for  example,  the  parietal  and  frontal 
eminences,  the  prominence  of  the  occiput,  and  the  nasion 
may  be  obscure,  and  the  superior  angles  of  the  frontal  and 
occipital  bones,  in  some  instances  displaced.  Experience 
and  judgment  is  as  essential  to  the  aspirant  for  success 
in  cerebral  surgery,  as  it  is  to  the  pelvic  surgeon,  who 
also  finds  in  the  pelvic  region  variations  which  must  influence 
his  judgment  in  particular  cases. 

In  devising,  therefore,  any  system  of  cerebral  localization, 
it  is  requisite  that  we  should  adopt  that  method  which  affords 
the  best  means  under  the  circumstances  of  selecting  the  most 
reliable  guides.  In  the  method  of  localization  here  presented, 
the  instrument  required  is  a  common  string,  which  is  always 
at  hand.  The  location  of  a  few  prominent  points  and  lines, 
which  are  easily  found  and  remembered,  is  all  that  is  neces- 
sary. These  are,  (see  figure  282):  the  nasion,  or  root  of  the 
nose;  the  occiput;  the  vertex,  which  is  midway  between  the 
latter  two  points;  the  prominences  of  the  angles  of  the  frontal 
and  the  occipital  bones,  situated  in  the  median  line  of 
the  head;  the  former  about  one  inch  and  a  half  in  front  of 
the  vertex,  and  the  latter  about  midway  between  the  vertex 


gitudi- 


Lobes  forming  the 


CEREBRAL    LOCALIZATION.  131 

and  the  occiput.  Other  points  are:  the  external  angular  pro- 
cess of  the  frontal  bone,  outer  canthus  of  the  eye,  inferior 
angle  of  the  malar  bone,  external  auditory  meatus,  and  the 
mastoid  process  of  the  temporal  bone. 

Beneath  the  median  line   of  the  skull,  from  the  nasion  to 
the  occiput,  is  the  superior  longitudinal  sinus,  and  the  longi-     Position  ot  th 
tudinal  fissure  separating  the  hemispheres  of  the  cerebrum 
The  calloso-marginal  fissure  emerges  from  the  median  fissure       '^^dlZllZlTJil 
a  little  behind  the  vertex,  and  the  anterior  arm  of  the  parieto-       j''','_''„^g""''  ^"^ 
occipital  fissure  reaches  the  surface  just  above  the  superior 
angle  of  the  occipital  bone.      The  upper  margins  of  the  lobes 
of  the  internal  surfaces  of  the  hemispheres  occupy  spaces 
along  the  median  line:  the  lingualis  and  cuneus  from  the  occi- 
put to  the  upper  angle  of  the  occipital  bone,  the  quadratus 
from  the  occipital  angle  nearly  to  the  vertex,  the  paracentral 
lobule  from  the  vertex  to  the  angle  of  the  frontal  bone,  and 
the  marginal  convolution  from  this  point  to  the  nasion. 

A  line  drawn  from  the  outer  canthus  to  the  center  of  the 
parietal  eminence  covers  the  -fissure  of  Sylvius,  and  if  contin- 
ued this  line  passes  through  the  crown  to  the  opposite  auditory 
meatus;  another  line  drawn  from  the  inferior  angle  of  the 
malar  bone  to  the  vertex  indicates  the  position  of  the  fissure 
of  Rolando. 

The  fissure  of  Sylvius  reaches  the  outer  surface  of  the 
hemisphere  at  the  intersection  of  these  lines,  and  divides  into 
a  short  anterior  arm  whicb  is  directed  upward  and  forward 
into  the  third  frontal  convolution,  and  a  long  or  posterior 
arm  which  extends  from  the  point  of  division  of  the  fissure, 
backward  and  upward,  to  the  middle  of  the  parietal  eminence. 
The  center  of  the  parietal  eminence  is  at  the  intersection  of  a 
line  from  the  vei'tex  to  the  auditory  meatus,  with  the  line 
marking  the  fissure  of  Sylvius. 

The  fissure  of  Rolando  begins  below,  about  the  middle  of 
the  posterior  arm  of  the  fissure  of  Sylvius,  and,  extending       roi 
directly  upward  for  a  short  distance,  reaches  the  before  men- 
tioned line  from  the  inferior  angle  of  the  malar  bone  to  the 
vertex,  under  the  upper  portion  of  which  it  lies.     The  anter- 


ines 

indicating 

tlie 

fissures  ot 

Syl' 

dus  and 

Rol 

ando. 

Fig. 

235^. 

ituai 

tionof  the 

lissi 

ire  of  Sylvius. 

Of  the  fissur 


132  ARCHITECTURE  OF  THE  BRAIN. 


Central  convolu 


Parietal  lob^ 


ior  and  posterior  central  convolutions  bound  the  margins  of 
the  fissure  of  Rolando.  The  frontal  convolutions  lie  beneath 
the  frontal  bone;    the  first  occupying  the  space  between  the 

■°'"-  frontal  eminence  and  the  median  line;  the  third,  surrounding 
the  anterior  arm  of  the  fissure  of  Sylvius,  lies  in  the  tem- 
poral fossa,  behind  the  external  angular  process.  The  inter- 
vening space  is  occupied  by  the  two  divisions  of  the  second 

Mvoiu-  frontal  convolution.  The  temporal  convolutions  lie  beneath 
the  fissare  of  Sylvius  and  extend  upward  and  backward  par- 
allel to  it.  The  supra  marginal,  or  second  parietal  convolu- 
tion, surrounds  the  posterior  extremity  of  tlie  Sylvian  fissure, 
and  occupies  the  region  of  the  parietal  eminence.      The  fir.-t 

■s.  parietal  lobule  is  above  the  parietal  eminence,  and  is  bounded 

above  by  the  margin  of  the  lobus  quadratus.  The  third  parietal 
convolution,  or  gyrus  angularis,  is  behind  and  slightly  above 
the  parietal  eminence,  in  front  of  the  lambdoid  suture.  Tlie 
occipital  convolutions  are  covered  by  the  occipital  bone,  and 
border  upon  the  cuneus  and  lingualis,  with  which  they  are 
connected. 

An  important  point  to  be  located  is  situated  above  and 
behind  the  auditory  meatus.  It  is  indicated  by  the  inter- 
section of  two  lines,  one  drawn  from  the  auditory  meatus  to 
the  superior  occipital  angle,  and  the  other  from  the  external 

"'^  angular  process  of  the  frontal  bone  to  the  occiput.  The  point 
border  of  iiitersectlon  marks  the  outer  extremity  of  the  lateral  siuus, 
and  also  the  outer  extremity  of  the  superior  border  of  the 
petrous  portion  of  the  temporal  bone,  which  divides  the  pos- 
terior from  the  middle  fossa  of  the  skull.  The  lateral  sinus 
is  directed  backward  from  this  point  to  the  occiput,  and  is 
usually  lower  down  upon  the  left  than  the  right  side  of  the 
head,  on  account  of  the  larger  size  of  the  left  hemisphere  of 
the  cerebrum,  and  the  smaller  size  of  the  left  hemisphere  of 
the  cerebellum. 

Figure  24  shows  the  situation  of  the  various  sensory  and 
motor  centers  of  the  convolutions,  according  to  Horsley;  and 
figure  25  the  same  after  Ferrier.  By  a  comparison  of  these 
figures,  it  will  be  observed  that  there  is  an  agreement  which 


;  pet; 
m  of  the 
)ral  bone, 


CEREBRAL    LOCALIZATION. 


133 


is  corroborative.  Figures  25  and  26  are  marked  by  vertical 
lines  into  thirty-six  sections,  which  are  one-sixth  of  an  inch 
apart,  and  numbered  to  correspond  with  those  of  the  figures 
that  follow  aftei'. 

By  the  use  of  the  topographical  sections,  it  will  be 
easy  to  study  the  relations  of  the  deeper  parts  to  the  surface 
of  the  braio;  and  by  a  comparison  of  successive  sections,  the 
dee  pel'  parts  may  be  traced  in  their  relations  to  each  other, 
and  compared  with  the  dissections  previously  studied  The 
directiou  in  which  a  trocar  may  be  thrust  with  safety,  and 
with  the  least  danger  of  injury  to  important  structures,  can  be 
determined  at  a  glance.  An  examination  of  these  sections 
creates  a  suprise  that,  in  so  short  a  distance  as  one-sixth  of  an 
inch,  tlie  configuration  of  the  successive  sections  present  so 
great  a  difference  in  appearance. 


The  location  of  the 
deeper  parts  of 
the  brain  by  the 
aid  of  topOKraph- 
ical  sections. 


Fiffiire  28^. 


Figure  24. 


TOPOrmAPHICAL  SECTIONS  OF  THE  BRAIN. 


External  Surface  of  the  Hemisphere. 

LOBES. 

Fl  F2  F3 — Frontal.  AC  and  PC — Anterior  and  posterior  central.  Tl  T2  T3 — Tem- 
poral. PI  P2  P3— Parietal.  P2 — Often  called  supraraarginal.  P3— Gyrus 
angularii.     01  02  03— Occipital. 

FISSURES. 
The  fissure  of  Sylvius  is  situated  above  and  along  the  first  temporal  lobe,  and  is 
indicated  by  a  line  drawn  on  the  surface  of  the  head  from  the  outer  canthus  of  the 
eye  to  the  parietal  eminence,  and  if  continued  the  line  would  pass  through  the  crown  to 
the  opposite  auditory  meatus.  The  fissure  of  Rolando  is  between  the  lobes  AC  and 
PC,  and  is  indicated  by  a  line  drawn  from  the  lower  angle  of  the  malar  bone  to  the 
vertex.  To  locate  the  lobes  and  fissures  along  the  longitudinal  fissure;  the  cuneu-S 
occupies  the  space  between  the  occiput  and  the  crown,  where  the  fissure  PO  reaches 
the  surface;  the  quadrate  lobe  extends  from  the  crown  to  the  vertex,  where  the  fissure 
CM  reaches  the  surface;  the  paracentral  lobule  extends  from  the  vertex  to  the  superior 
angle  of  the  frontal  bone;  the  frontal  bone  covers  the  marginal  convolution.  These 
directions  though  not  exact  are  sufiicient  for  practical  purposes  and  are  quite  as  relia- 
ble as  any  of  the  expensive  contrivances  in  use  for  locating  these  parts.  The  outer 
portion  of  the  Great  Transverse  fissure  is  between  the  occipital  lobes  and  the  cere- 
bellum. 

PSYCHOMOTOR    CENTERS.     (From  Ferrier.) 

1.  Advance  ofthe  opposite  hind  limb  as  in  walking 

2,  3,  4.     Complex  movements  of  the  opposite  leg  and  arm  and  of  the  trunk,  as  in  swim- 

ming. 
a,  b,  c,  d.     Individual   and  combined   movements   of    the   fingers  and    wrist    of    the 
opposite  hand.     Prehensile  movements. 

5.  Extension  forward  of  the  opposite  arm  and  hand. 

6.  Supination  and  flexion  of  the  opposite  forearm. 

7.  Retractio;;  and  elevation  of  the  opposite  angle  of  the  mouth  by  means  of  the 
zygomatic  muscles. 

8.  Elevation  of  the  alae  nasi  and  upper  lip  with  depression  of  the  lower  lip  on  the 
opposite  side. 

9.  10.     Opening  of  the  mouth  with  (9)  protrusion,  and  (lOj  retraction  of  the  tongue. 

Region  of  Aphasia. 

11.  Retraction  of  the  opposite  angle  of  the  mouth,  the  head  turned  slightly  to  one 
side. 

12.  Eyes  open  widely,  pupils  dilating,  and  the  head  and  eyes  turning  towards  the 
opposite  side. 

13.  14.     The  eyes  moving  towards  the  opposite  side  with  an  upward  (13), or  downward 

(14)  deviation.     Pupils  generally  contracting.     (Center  of  vision  ) 
15.     Pricking  up  of  the  opposite  ear.  head  and  eyes  turning  to  the  opposite  side,  and 
pupils  dilating  largely.     (Center  of  hearing.) 
136 


Fisrure  25, 


TOPOGRAPHICAL  SECTIONS  OF  THE  BRAIN. 


(These  sectios  are  cut  sis  to  the  inch,  and  the  plates  are  made  from  photograph  of  the  sections.) 

Median  Section  along  tlie  Great  Longitudinal  Fissure. 

LOBES. 

L — LiDgualis.      C— Cuneus.      Q— Quadratus.       QF— Gyrus   fornicatus.      PC — Para- 
central.    MM — Marginal. 

FISSURES. 

The  fissure  of  Bichat,  or  the  Great  Transvers  fissure,  is  between  the  lingual  lobe 
and  the  cerebellum.  The  Calcarine  fissure  is  between  L  and  C.  The  Parieto-occip- 
ital  fissure  is  between  C  and  Q  The  Calloso-marginal  fissure  is  bounded  by  the  lobes 
Q  and  GF  below,  and  PC  and  MM  above.  The  fissure  called  the  Ventricle  of  the 
Corpus  Callosum  is  between  GF  and  CC. 

COMMISSURES,    ETC. 

CC— Corpus  callosum.  F  — Fornix.  SL- Septum  lucidum.  Beneath  F  is  the 
intraventricular  portion  of  the  Great  Transverse  fissure,  through  which  passes  the 
velum  interpositum  from  the  third  to  the  lateral  ventricle,  its  anterior  extremity  is 
called  the  Foramen  of  Monro.  AC — Anterior  commissure.  MC — Middle  commis- 
sure. P -Pineal  gland,  its  anterior  pillars  extending  forwards  below  the  fornix.  In 
front  of  and  beneath  P,  is  the  posterior  commissure.  TN— Corpora  quadrigemina 
— T  is  on  the  testes,  and  N  on  the  nates.  Beneath  T  and  N  is  the  iter.  CE  -Cere- 
bellum. Between  CE  and  T  is  the  valve  of  Vieussens,  beneath  which  is  the  cavity  of 
the  fourth  ventricle.  Above  and  below  the  valve  are  the  superior  and  inferior 
vermiform  processes.  R  -Restiform  body,  beneath  which  is  the  central  canal  of  the 
cord  DP — Decussation  anterior  pyramids  N— Pons  Varolii.  FT — Fillet  or  lem- 
niscus. Between  FT  and  the  fourth  ventricle  is  the  fasciculi  teretes.  PT — Decussa- 
tion of  the  processes  testes.  RN— Cms  cerebri,  the  letters  are  over  the  red  nucleus. 
3 —Third  nerve.  CA- Corpora  albicantia.  I  — Infundibulum  and  tuber  cinereum. 
O — Optic  commissure  Between  O  and  AC  is  the  lamina  cinerea,  in  front  of  which 
is  the  anterior  pillar  of  the  the  corpus  callosum. 


1Q» 


Figure  26. 


140 


ARCHITECTURE    OF    THE    BRAIN. 


■'X 


No.    1. 


"%yf> 


No.  2. 


M  and  M — Marginal  conv. 
f  1  fS  fS — Frontal   convolu- 
tions. 
'0 — Orbital  convolution. 


TOPOGRAPHICAL    SECTIONS    OF    THE    BRAIN.  141 


No.    3. 


No.    4. 


M  and  M — Marginal  conv. 
Fi  F^  r»  —Frontal   convolu- 
tions. 
0 — Orbital  convolution. 


142 


ARCHITECTURE    OF    THE    BRAIN. 


No. 


Gf  r — GjTus  fornicatus. 
M  and  M — Marginal  conv. 
f  1  ^2  fS — Frontal   convolu- 
tions. 
0 — Orbital  convolution. 


TOPOGRAPHICAL    SECTIONS    OF   THE    BRAIN. 


143 


No.  6. 


Of  F — Gyrus  fornicatus. 

M  and  M — Marginal  conv. 
fifsps — Frontal   convolu- 
tions. 
0 — Orbital  convolution. 


144 


ARCHITECTURE    OF    THE    BRAIN. 


No.    7. 


C  C — Corpus  callosum. 
Of  F — Gyrus  fornicatus. 
M  and  M — Marginal  conv. 
j'lj'aj'S — Frontal   convolu- 
tions. 
0 — Orbital  convolution. 


TOPOGRAPHICAL    SECTIONS    OF   THE   BRAIN. 


145 


No.    8. 


CC  -Corpus  callosum. 
G  F — Gyrus  fornicatus. 
M  M — Marginal  convolution. 
f  1  Y^  F*  — Frontal  convolu- 
tions. 


0 — Orbital  convolution. 
V — Anterior  cornu  of  lateral 
ventricle. 


146 


ARCHITECTURE    OF    THE    BRAIN. 


No.   9. 


CC^  Corpus  callosiim. 
Gr  F — Gyrus  fornicatus. 
M  M — Marginal  convolution. 
pi  p2  j,-3  — Frontal  convolu- 
tion. 
0 — Orbital  convolution. 


Y — Anterior  cornu   of  lateral 

ventricle. 
N  C — Nucleus  caudatus. 
C  L — Claustrum. 
In — Insula,  or  island  of  Riel. 
S' — Fissure  of  Sylvius. 


TOPOGRAPHICAL    SECTIONS    OF    THE    BRAIN. 


147 


No.  10. 


CC  and  ec — Corpus  callosum. 
G  F — Gyrus  fornicatus. 
M  and  M — Marginal  conv. 
pi  F2  J13  _Frontal   convolu- 
tions. 
0 — Orbital  convolution. 


V — Lateral  ventricle. 

N  C — Nucleus  caudatus. 

I  C     Internal  capsule. 

C  L — Claustrum. 

In  — Insula,  or  island  of   Riel. 

S  and  S—  Fissure  of  Sylvius. 


148 


ARCHITECTURE    OF    THE    BRAIN 


No.  11. 


CC  and  (•(  — Corpus  callosum. 

a  P — Gyrus  fornicatus. 

M — Marginal  convolution. 

pi  F^  F*  — Frontal  convolu- 
tions. 

T^  — First  temporal  convolu- 
tion. 

0 — Orbital  convolution. 


V — Lateral  ventricle. 

N  C — Caudate  nucleus. 

I  C — Internal  capsule. 

N  L — Lenticular  nucleus. 

X — External  capsule. 

C  L — Claustrum. 

In — Insula,  or  island  of  Riel. 

S  and  S — Fissure  of  Sylvius. 


TOPOGRAPHICAL   SECTIONS    OF   THE    BRAIN. 


149 


No.  12. 


CC  and  CC — Corpus  callosum. 
Gr  F — Gyrus  fornicatus. 
M — Marginal  convolution, 
f  1  f  2  j"3  — Frontal    convolu- 
tions. 
A  F — Ascending  frontal  conv. 
rpi  ffi  fpa  — Temporal  convs. 
0 — Orbital  convolution. 


V — Lateral  ventricle. 

N  C — Nucleus  caudatus. 

I  C — Internal  capsule. 

N  L — Nucleus  lenticularis. 

X — External  capsule. 

C  L — Claustrum. 

In — Insula,  or  island  of  Riel. 

S  and  S— -Fissure  of  Sylvius. 


150 


ARCHITECTURE    OF    THE    BRAIN.    | 


No,  13. 


C  C — Corpus  callosum. 
G  F — Gyrus  fornicatus. 
CM — Calloso-marginal  fissure 
M — Marginal  convolution. 
pi  f  3  ps  Frontal  convs. 
A  F — Ascending  frontal  conv. 
K- — Fissure  of  Rolando. 
rpi  7-2  rj-s  —Temporal  convs 
0 — Optic  nerve. 
S  P-  Substantia   perforata 
anterior. 


V — Lateral  ventricle. 

N  C — Nucleus  caudatus. 

I  C — Internal  capsule. 

N  L — Nucleus  lenticularis. 

X — External  capsule. 

C  L — Claustrum. 

In — Insula,  or  Island  of  Riel. 

S  and  S — Fissure  of  Sylvius. 


TOPOGRAPHICAL    SECTIONS    OF    THE    BRAIN. 


151 


No.  14. 


C  C — Corpus  callosum. 

G  F — Gyrus  fornicatus. 

C  M — Calloso-marginal  fissure 

M — -Marginal  convolution. 

fi  pa  ps  — Frontal  convs. 

A  F — Ascending    frontal    or 

central  convolution. 
R — Fissure  of  Rolando. 
rpi  X^  T*  —Temporal  convs. 
F  M — Fusiform  convolution 
H  —  Hippocampal  conv. 
g  P — Substantia  perforata. 


0 — Optic  nerve. 

L  C — Lamina  cinerea. 

A  C — Anterior  commissure. 

F — Anterior  pillar  fornix. 

V — Lateral  ventricle. 

N  C — Caudate  nucleus. 

I  C— -Internal  capsule. 

N  L — Lenticular  nucleus. 

X — External  capsule. 

C  L — Claustrum. 

In — Insula,  or  island  of  Riel. 

S  and  S—  Fissure  of  Sylvius. 


152 


ARCHITEOTURE    OF   THE   BRAIN. 


No.  15. 


C  C — Corpus  callosum. 

G  F — Gyrus  fornicatus. 

C  M — Calloso-marginal  fissure 

M — Marginal  convolution. 

pi  F^F*  — Frontal    convs. 

A  F — Ascending    frontal      or 

central  convolution. 
R  R — Fissure  Rolando. 
XI  T^T"— Temporal  convs. 
F  M — Fusiform  convolution. 
H — Hippocampal  convolution 
S  P — Substantia  perforata. 
0 — Optic  commissure. 
Lc — Lamina  cinerea. 


F  and  F — Fornix. 

T*  — Third  ventricle. 

V — Lateral  ventricle. 

N  C — Caudate  nucleus. 

I  C — Internal  capsule. 

LN — Lenticular  nucleus.  1, 
2,  .3,  its  three  divisions. 

AC — Divided  outer  extrem- 
ity of  the  anterior  commis- 
sure. 

X — External  capsule. 

C  L — Claustrum. 

In — Insula. 

S  and  S — Fissure  Sylvius. 


TOPOGRAPHICAL    SECTIONS    OF    THE    BRAIN. 


153 


No.  16. 


C  C — Corpus  callosum. 

Gr  F — Gyrus  fornicatus. 

C  M — Calloso-marginal  fissure 

P — Paracentral  lobule. 

pi  — First  frontal  conv. 

A  C — Anterior  central  or  as- 
cending frontal. 

PC — Posterior  central  or  as- 
cending parietal. 

R — Fissure  of  Rolando. 

S  M — Supramarginal  or  sec- 
ond parietal  lobule. 

rpi  rji-2  rjig  — Temporal  convs. 

FM — Fusiform  convolution. 

H — Hippocampal  conv. 


SPP — Substantia    perforata 

posterior. 
0 — Optic  tract. 
T  C — Tuber  cinereum. 
F  and  F — Fornix. 
V^  — Third  ventricle. 
Y — Lateral  ventricle. 
N  C — Tail  of  caudate  nucleus. 
T  H — Thalamus  opticus. 
IC  and  IC — Internal  capsule. 
LN  '  "'  ^ — Lenticular  nucleus. 
X — External  capsule. 
C  L — Claustrum. 
Ill — Insula,  or  island  of  Riel. 
S  and  S — Fissure  of  Sylvius. 


154 


ARCHITECTURE    OF    THE    BRAIN. 


No.  17. 


CC — Corpus  callosum. 

G  F — Gyrus  fornicatus. 

CM — Calloso-marginal  fissure 

P — Paracentral  lobe. 

RandR — Fissure  of  Rolando. 

AC  and  PC — Anterior  and 
posterior  central  convs. 

S  M — Supramarginal  or  sec- 
ond parietal  convolution. 

iji  fS  fj^s  — Temporal  convs. 

FM — Fusiform  convolution. 

H — Hippocampal  conv. 

VM  -  Middle  cornu  of  lateral 
vent,  and  pes  hippocampi. 

SPP — Substantia  perforata 
posterior. 

0 — Optic  tract. 


C  A — Corpus  albicantia. 

T*  — Third  ventricle.  The 
letter  rests  upon  the  grey 
matter  of  its  wall  opposite 
the  middle  commissure. 

F — Fornix. 

V — Lateral  ventricle. 

N  C — Tail  of  caudate  nucleus. 

T  H— Thalam.us. 

IC  and  IC — Internal  capsule. 

LN^  2  3  — Lenticular  body;  its 
three  divisions. 

X — External  capsule. 

C  L — Claustrum. 

In — Insula,  or  island  of  Riel. 

S  and  S— Fissure  of  Sylvius. 


TOPOGRAPHICAL    SECTIONS    OF    THE    BRAIN.  155 


No.  18. 


CI  C — Corpus  callosum. 

G  F-  -Gyrus  fornicatus. 

C  M — Colloso-marginal  fissure 

P — Paracentral  lobule. 

AC  and  PC — Anterior  and 
posterior  central  convs. 

R — Fissure  of  Rolando. 

S  M — Supramarg.  conv. 

rpi  rj"2  rps  —  Tempore   sphe- 
noidal, or  temporal  convs. 

F  M — Fusiform  convolution. 

H — Hippocampal.  The  letter 
rests  upon  the  cornu  Am- 
monis. 

V  M— Middle  cornu  lat.  vent. 

0 — Optic  tract. 

S  N — Substantia  nigra  of  crus 
cerebri,  and  external  to  SN 
are  the  fibres  of  the  crusta 
passing  upward   to  the  in- 


ternal capsule. 

V^--Wall  of  third  ventricle. 

F — Fornix. 

y — Lateral  ventricle. 

N  C  and  N  C — Tail  of  caudate 
bod}';  •  the  lower  NC  is  ex- 
ternal to  O  and  is  the  lower 
extremity  of  the  tail  of  the 
caudate  body,  situated  in 
the  roof  of  the  middle  cornu 
of  the  lateral  ventricle. 

IC  and  IC — Internal  capsule; 
the  lower  IC  are  the  fibres 
of  the  capsule  distributed 
to  the  temporal  lobes. 

jj  jj  12  3 — Lenticular  body. 

X — External  capsule. 

C  L — Claustrum. 

In — Insula,  or  island  of  Riel. 

S — Fissure  of  Sylvius, 


156 


ARCHITECTUEE    OF   THE   BRAIlf. 


No.  19. 


C  C — Corpus  callosum. 

(j  F — Gyrus  fornicatus. 

C  M— Calloso-marginal  fissure 

P — Paracentral  lobe. 

A  C  and  'P  C — Anterior  and 
posterior  central  convs. 

R — Fissure  of  Rolando. 

S  M — Supra  marginal  conv. 

Ti  T^  T**  —Temporal  convs. 

F  M — Fusiform  lobe. 

H — Hippocampal. 

VM — Middle   cornu   lateral 
ventricle. 

0 — Optic  tract. 

SN — Substantia  nigra,  or  lo- 
cus niger.  The  crusta  is 
external  to  SN,  and  is  con- 
tinuous with  IC. 


II  N — Red  nucleus,  running 
out  from  which  is  the  fillet. 

ys  —Wall  of  third  ventticle. 

F — Fornix. 

Y — Lateral  ventricle. 

NC  and  N€ — Caudate  nucleus. 

TF — Thalamus. 

IC,  IC,  IC — Internal  capsule. 
The  row  of  dark  spots  be- 
tween the  upper  and  lower 
IC  is  the  posterior  extrem- 
ity of  the  lenticular  nucleus. 

In — Insula,  or  island  of  Riel. 

S — Fissure  of  Sylvius.  A 
trace  of  the  claustrum  can 
be  seen  in  this  section. 


TOPOGRAPHICAL    SECTIONS    OF   THE    BRAIN. 


157 


No.  20. 


CC — Corpus  collosum. 

GrF — Gyrus  fornicatus. 

C  M — Calloso-marginal  fissure 

P — Paracentral  lobe. 

AC  and  PC — Anterior  and 
posterior  central  convs. 

R — Fissure  of  Rolando. 

P^  — Paracentral  lobe. 

S  M — Supramarginal  conv. 

XI  T"  T*  —Temporal,  or  tem- 
pero  sphenoidal  convs. 

F  M — Fusiform. 

H — Hippocampal  convolu- 
tion, or  cornu  Ammonis,  the 
projection  of  which  into  the 
middle  cornu  of  the  lateral 
ventricle  forms  the  hippo- 
campus major. 

V  M— Middle  cornu. 


G  G — Corpus  geniculata,  ex- 
ternal and  internal,  which 
are  the  termination  of  the 
two  roots  of  the  optic  tract. 

N — Pons  Varolii. 

S  N — Substantia  nigra. 

R  N — Red  nucleus,  which  is 
connected  b)'  a  grey  com- 
missure with  another  round 
grey  mass  above,  and  inter- 
nal to  the  letters  TH. 

ys  — Third  ventricle. 

F — Fornix. 

V — Lateral  ventricle. 

NC  and  NC — Caudate  nucleus. 

T  H — Thalamus,  displaying  a 
peculiar  radiation  of  fibres. 

IC  and  IC — Internal  capsule 
at  its  genu. 

S — Fissure  of  Sylvius. 


158 


ARCHITECTURE    OF    THE    BRAIW. 


No.  21. 


C  C — Corpus  callosum. 

Gr  F — Gyrus  fornicatus. 

Q — Quadratus  or  precuneus 
lobe. 

C  M — Calloso-marginal  fissure 

P.  and  AC — Union  of  para- 
central and  anterior  central 
convolutions. 

R — Fissure  of  Rolando. 

P  C — Poterior  central  or  as- 
cending parietal  conv. 

pi  — First  parietal  lobule. 

P^  and  S  M — Second  parietal 
lobule  or  supra  marginal 
convolution. 

rpi  rp2  ff  s — Temporal  convs. 

F  M — Fusiform  convolution. 

H — Hippocampal  lobe. 

Y  M — Middle  cornu  and  hip- 
pocampus major;  and  direct- 
ed toward  G  G  is  the  corpus 


fimbriatum  or  edge  of  the 
fornix,  forming  the  lower 
boundary  of  the  fissure  of 
Bichat,  through  which  the 
velum  enters  the  lateral 
ventricle. 

G  G — Corpora  geniculata,  con- 
tinuous below  with  the  optic 
tract  and  behind  with  the 
pulvinar. 

P — Pulvinar. 

N — Pons. 

F  T— Fillet  tract. 

S  N — Substantia  nigra. 

P  T — Processus  testes. 

C  P — Posterior  commissure. 

F — Fornix. 

V — Lateral  ventricle. 

NC  and  NO — Caudate  nucleus. 

I  C  and  IC — Internal  capsule. 

S — Fissure  Sylvius. 


TOPOGRAPHICAL    SECTIONS    OF   THE   BEAIN 


1591 


No.  22. 


C  C — Corpus  callosum. 

GrF — Gyrus  fornicatus. 

Q — Lobus  quadratus. 

C  M — Calloso-marginal  fissure 

P  and  AC — Paracentral    and 

ascending  frontal. 
R — Upper    end  of    fissure  of 

Rolando. 
P  C — Posterior  central  conv. 
pi . — First  parietal  lobule. 
p2andS)I — Second    parietal 

lobe. 
rpi  rji3  rps  — Temporal  convs. 
F  M — Fusiform  conv. 
H — Hippocampal  conv.  at  its 

junction  with  the   lingualis 

and  gyrus  fornicatus. 
N — Pons  Varolii. 
FT — Fillet  or  lemniscus. 
P  T — Processus  e  cerebello  ad 

testes  at  its  decussation. 


IT— Iter. 

N  A— Nates. 

P — Pineal  gland. 

T,v — Lvra. 

P  y — Pulvinar,  or  optic  centre 

ot  ine  tnaiaiuus. 
TH— Thalamus. 
F   and   F — Fornix,    winding 

around  the  posterior  part  of 

the  thalamus. 
Y — Lateral  ventricle. 
NC  and  NC— Genu  of  the  tail 

of  the  caudate  nucleus. 
YJI — Middle  cornu  of  the  lat- 
eral ventricle. 
I  C — Posterior   fibres    of   the 

Internal  capsule. 
L — External   longitudinal 

commissure. 
S — Fissure  of  Sylvius. 


160 


ARCHITECTURE    OF    THE    BRAIK^. 


No.  23. 


C  C — Corpus  callosum. 

G  F — Gyrus  fornicatus. 

Q — Lobus  quadratus. 

C  M — Calloso-marginal  fissure 

P — Paracentral  lobule. 

R — Fissure  of  Rolando. 

P  C — Ascending    parietal    or 

posterior  central  conv. 
Pi — First  parietal  lobule. 
P* — Third  parietal  lobule  or 

gyrus  angularis. 
P- — Second  parietal  lobule. 
fji  ^[2  fs  — Temporal  convs. 
F  M — Fusiform  lobe. 
L  G — Lobus  lingualis. 
C — Cerebellum. 
N— Pons. 
FT — Fillet  or  lemniscus. 


P  T — Processus  e  cerebello  ad 
testes. 

I  T — Iter  e  tertio  ad  quartum 
ventriculum. 

T — Testes. 

VP — Posterior  cornu  of  the 
lateral  ventricle. 

Y  31 — Middle  cornu  of  the 
lateral  ventricle. 

IC  Posterior  distribution  of 
fibres  of  the  internal  cap- 
sule. 

L — External  longitudinal 
commissure,  separated  from 
the  sub-convolutional  la}'er 
of  the  corona  radiata  by  a 
delicate  arched  white  line. 


TOPOGRAPHICAL    SECTIONS    OF    THE    BRAIN. 


161 


C  C — Corpus  callosum. 

GrF  and  GF — Gyrus  fornicatus 

Q — Lobus  quadratus  or  pre- 
cuneus. 

C  31 — Calloso-marginal  fissure 

P  and  PC — Junction  of  para- 
central and  post,  central 
convolutions. 

Pi  ■ — First  parietal  lobe. 

P^  — Gj'rus  angularis. 

rj\2  ff  3  , — Temporal  convs. 

F  M— Fusiform  lobe. 

L  (t — Lingualis. 

YP  and  TM— Junction  of  the 
posterior  with  the  middle 
cornu  of  the  lateral  ventricle 

L — Ext.  longitudinal  comm. 

I  C — Internal  capsule. 

P  T — Processes  testes. 

N — Lateral  fibres  of  pons. 


R — Restiform     fibres    of    me- 
dulla oblongata. 
FT— Fillet. 

P  R — Anterior     pyramids     of 
the  medulla. 

The  composition  of  the 
corona  radiata  is  well  seen  in 
this  plate.  The  fibres  of  the 
corpus  callosum  are  internal 
to  the  ventricle;  the  decussa- 
tion between  its  fibres  and  the 
internal  capsule  is  above, 
while  the  outer  wall  of  the 
ventricle  is  formed  by  the  in- 
ternal capsule,  separated  from 
L  by  a  dark  line.  External 
to  L  is  the  sub-convolutional 
white  fibres,  or  internuncial 
layer  of  the  corona  radiata. 


162 


ARCHITECTURE    OF    THE    BRAHf. 


No.  25. 


L — External  longitudinal 
commissure. 

V  P — Posterior  cornu.  Be- 
tween L  and  V  P  are  fibres 
of  the  internal  capsule  di- 
rected backward  to  the 
cuneus  and  occipital  lobtf, 
containing  optic  fibres. 

C  C — Posterior  fibres  of  the 
corpus  collosum. 

P  0 —  Commencement  of  the 
parieto-occipital  fissure. 

GF  and  GF— Gyrus  fornicatus 

Q — Lobus  quadratus. 

C  M  —Calloso-marginal  fissure 

pi  —First  parietal  lobule. 

P^  — Lobus  angularis. 

P'^  — Supra-marginal  or  sec- 
ond parietal  lobule. 


IJ2  rps  — Temporal    convolu- 
tions. 

F  H — Fusiform  convolution. 

L  G  —  Lingualis. 

C — Cerebellum. 

N — Lateral  fibres  of  pons. 

R — Restiform  body. 

0 — Olivary  body. 

P  R — Anterior  pyramid. 

F  T— Fillet. 

T — Fasciculus  teretes. 

P  T — Processes  testes  and 
fourth  ventricle.  The  valve 
of  Vieussens  forms  the  roof 
of  the  fourth  ventricle  by 
uniting  the  upper  part  of 
one  processus  with  the 
other. 


TOPOGRAPHICAL    SECTIONS    OF    THE    BRAIN. 


163 


No.  26. 


L — External   longitudinal 
commissure  and  internal 
capsule. 

y  P — Posterior  cornu. 

PO — Parieto-occipital  fissure. 

Q — Lobus  quadratus. 

pi  — First  parietal  conv. 

ps — Angular  lobe. 

rf2X3 — Temporal  convs. 

F  M — Fusiform  convolution. 


L  G—  Lingualis  convolution. 
C — Cerebellum. 
N  —  Pons,  lateral  fibres. 
P  T — Processus  testes. 
R — Restiform  body. 
T — Fasciculus  teretes. 
F  T — Fillet  or  lemniscus. 
0 — Olivary  bod}'. 
PR  —  Anterior    p3-ramids    of 
medulla. 


164 


ARCHITECTURE    OF    THE    BRAIN. 


No.  27. 


L — External    longitudinal 
commissure. 

VP — Posterior  cornu  and  in- 
ternal capsular  fibres. 

PO     Parieto-occipital  fissure. 

Q — Lobus  quadratus. 

pi  ps  —Parietal  lobes. 

rf2  rps  — Temporal    convolu- 
tions. 


F  M — Fusiform  convolution. 

L  G — Lingualis. 

C — Cerebellum. 

D — Corpus  dentatum. 

R — Restiform  body. 

The  olivary  body  and  an- 
terior pyramids  are  seen  be- 
neath R. 


TOPOGRAPHICAL    SECTIONS    OF    THE    BRAIN. 


166 


S^A  1^'     \  J  It  / ,  ''^r'*.-t  i«^< 


No.  28. 


L- — External    longitudinal 

commissure. 

Posterior  fibres  of    the 

internal  capsule,  posterior 

cornu. 
Po — Parieto-occipital  fissure. 
C — Apex  of  cuneus. 
Q — Quadratus  or  precuneus. 


Pi  ps.  ~  Parietal  lobes. 

rji2  rps  — Temporal  lobes. 

F  M — Fusiform  convolution. 

L  G —  Lingualis. 

D—  Corpus  dentatum. 

To — Tonsil. 

U— Uvula. 

R — Restiform  body. 


166 


ARCHITECTURE   OF    THE    BRAIN 


»:,, 


"^1  'if 
No.  29. 


L — External   longitudinal 
commissure,  internal  cap- 
sule, cornu  lateral  ventricle. 

C  A — Calcarine  fissure. 

C^ — Cuneus  lobe. 

Po — Parieto-occipital  fissure. 

Q — Quadratus  lobe. 


pi  ps  _Parietal  lobes. 
'J2  f  3  — Temporal  lobes. 
F  M-  Fusiform  lobe. 
L  6 — Lingual  lobe. 
D— Corpus  dentatum. 
To— Tonsil. 
XJ_Uvula. 


TOPOGRAPHICAL    SECTIONS    OF    THE    BRAIN. 


167 


No.  30. 


L — External    longitudinal 
commissure,  extremity  of 
posterior  cornu. 

C  A — Calcarine  fissure. 

C — Cuneus. 

Po— Parieto-occipital  fissure. 


Q — Precuneus  or  quadratus. 
Qi  02  O'*  -  Occipital  lobes. 
T^  — Third  temporal  conv. 
F  M — Fusiform. 
L  G — Lingualis. 
D — Dentate  body. 


168 


ARCHITECTURE    OF    THE    BRAIN. 


No.  31. 


L — External  longitudinal 
commissure,  posterior 
cornu. 

C  A—  Calcarine  fissure. 

C — Cuneus. 


Qi  0-  0^  —Occipital  lobes. 
'1* — Third  temporal 
F  M— Fusiform. 
L  G — Lingualis. 


TOPOGRAPHICAL    SECTIONS    OF    THE    BRAIN. 


169 


No.  32. 


C  A — Calcarine  fissure. 

C — Cuneus. 

Qi  0-  OS  —Occipital  lobes. 


T*  — Third  temporal. 
F  M — Fusiform. 
L  €r — Lingualis. 


170 


ARCHITECTURE    OF    THE    BRAIN. 


No.  33. 


C  A — Calcarine  fissure. 

C — Cuneus. 

0*  0^  0^  — Occipital  convs. 

F  M — Fusiform. 

L  G — Lingualis. 


TOPOGRAI'HICAL    SECTIONS    OF    THE    BRAIN. 


171 


No.  34. 


C — Cuneus. 

0^  0^  0^  -   Occipital  convs. 

F  M — Fusiform. 

L  G — Lingualis. 


172 


ARCHITECTURE    OF   THE    BRAIN. 


No.  35. 


C — Cuneus. 

Ql  02  0^  -  Occipital  convs. 

F  M — Fusiform. 

L  6 — Lingualis. 


TOPOGRAPHICAL    SECTIONS    OF    THE    BRAIN. 


173 


'^g^.' 


No.  36. 


C — Cuneus. 

Ql  02  QS  ^   Occipital  convs. 

F  M — Fusiform. 

L  G — Lingualis. 


174  AECHITECTURE    OF   THE    BEAEST. 


Figure  27  represents  the  upper  surface  of  the  cerebellum, 
and  a  section  of  the  crura  cerebri  through  the  nates  forward 
to  the  posterior  perforated  space.  Tue  nates  are  united  by  a 
commissure  above  the  iter.  The  roof  of  the  iter  is  arched, 
and  its  floor  is  formed  by  the  fasciculi  teretes,  which  are 
divided  in  the  middle  line  by  the  central  fissure.  A  section 
of  the  raphe  dividing  the  cruri  cerebri  extends  from  the  me- 
dian fissure  of  the  iter  to  the  posterior  perforated  space. 
Surrounding  the  iter  is  a  layer  or  tube  of  grey  matter,  which 
is  the  continuation  of  the  grey  columns  of  the  spinal  cord 
and  the  grey  matter  of  the  floor  of  tlie  fourth  ventricle. 
Downward  and  outward  from  the  grey  matter  around  the  iter, 
in  succession  upon  each  side,  are  sections  of  the  processus, 
fillet,  locus  niger,  and  crusta.  External  to  these  parts,  upon 
a  line  with  the  nates  on  each  side,  are  the  brachia.  The 
third  nerve  enters  the  inner  side  of  the  crus  cerebri, divides 
into  strife,  which  spread  as  they  pass  through  the  fibres  of  the 
processus  to  reach  the  grey  matter  of  the  iter.  That  portion 
of  the  section  above  the  crustte,  including  the  locus  niger,  is 
called  the  tegmentum.  The  broad  notch  in  front  of  the  cere- 
bellum embracing  the  tegmentum,  is  called  the  incisura 
anterior,  and  the  notch  behind,  the  incisura  posterior.  Be- 
tween these  notches  is  an  elevated  portion  of  the  cerebellum, 
the  superior  vermiform  process,  or  middle  lobe  of  the  cere- 
bellum; its  middle  portion  is  called  the  monticulus,  a  small 
lobe  in  the  incisura  anterior  is  called  the  lobus  centralis,  and 
a  few  transverse  convolutions  behind  are  named  the  commis- 
sura  simplex.  The  superior  vermiform  process  is  continuous 
behind  with  the  inferior  vermiform  process  of  the  middle 
lobe  (Fig.  29).  The  lateral  portion  of  the  upper  surface  of 
the  cerebellum  contains  two  lobes;  the  square  lobe  in  front, 
and  the  semilunar  lobe  behind. 


Figure  27'. 


176  AECHITECTUBE    OF    THE    BKAIN. 


Figure  28 — Is  an  anterior  view  of  the  cerebellum,  showing 
its  hilua  and  the  relations  of  the  parts  transmitted  by  it,  and 
also  a  section  of  the  fourth  ventricle.  Above  the  hilus  is  the 
elevated  middle  lobe  of  the  cerebellum,  concave  in  front  to 
embrace  the  crura  cerebri,  called  the  incisura  anterior.  In 
the  middle  of  the  notch  is  a  small  lobe,  the  lobus  centralis, 
which  is  the  anterior  extremity  of  the  superior  vermiform 
process,  and  rests  upon  the  upper  surface  of  the  valve  of 
Vieussens.  Beneath  the  valve  is  the  cavity  of  the  fourth 
ventricle,  containing  the  nodule,  which  is  the  anterior  extrem- 
ity of  the  inferior  vermiform  process,  and  is  in  relation  with 
the  under  surface  of  the  valve  of  Vieussens.  The  nodule  is 
connected  on  either  side  with  the  flocculus,  by  a  thin  mem- 
brane called  the  commissure  of  the  flocculi.  Beneath  the 
nodule  are  the  other  parts  comprising  the  inferior  vermiform 
process,  viz:  the  uvula,  pyramid,  and  commissura  brevis. 
Upon  each  side  of  the  uvula  are  the  amygdalae  or  tonsils, 
external  to  which,  on  either  side,  are:  the  flocculus,  digasti'ic, 
slender,  and  the  posterior  inferior  lobes,  of  the  lateral  mass  of 
the  cerebellum.  The  lateral  lobes  are  divided  by  a  deep  notch 
extending  from  the  roof  of  the  fourth  ventricle  to  the  pos- 
terior part  of  the  cerebellum,  the  incisura  posterior. 

The  par.s  transmitted  by  the  hilus  are  from  within  out- 
ward: the  valve  of  Vieussens,  processes,  restiform  bodies, 
and  the  pons,  composed  of  a  deep  and  superficial  layer  of 
fibres.  These  parts  compose  the  crura,  or  peduncles  of  the 
cerebellum,  beneath  which  are  the  flocculi  on  each  side. 
The  convolutions  and  fissures  of  the  cerebellum  radiate  from 
the  hilus,  and  the  great  transverse  fissure  of  the  cerebellum 
is  seen  extending  out  laterally  from  each  crus;  and,  being 
continuous  behind,  divides  the  cerebellum  into  superior  and 
inferior  lobes. 


't^/^ 


^l>^. 


Fisure  28. 


178  ARCHITECTURE    OF    THE    BRAIN, 


Figure  29 — Is  a  representation  of  the  under  surface  of 
tlie  cerebellum.  Above  and  in  front  is  tlie  iucisura  anterior, 
upon  each  side  of  which  is  the  flocculus.  Behind  is  the  in- 
cisura  posterior,  and  extending  along  the  middle  of  the  under 
surface  of  the  cerebellum,  between  the  incisurse,  is  a  deep 
furrow,  at  the  bottom  of  which  is  the  inferior  vermiform 
process  of  the  middle  lobe  of  the  cerebellum,  the  parts  of 
which,  from  before  backward,  are:  the  nodule,  uvula,  pyra- 
mid, and  commissura  brevis.  The  inferior  surface  of  the 
lateral  hemisphere  of  the  cerebellum  contains  from  within 
outward:  the  tonsil,  digastric,  slender,  and  posterior  inferior 
lobes.  Behind  the  commissura  brevis  and  the  posterior  in- 
ferior lobes,  is  the  great  transverse  fissure  of  the  cerebellum, 
which  divides  the  upper  from  the  lower  surfaces.  The 
separation  of  the  sides  of  this  fissure  from  behind  uncovers 
the  dentate  bodies  which  adhere  to  the  inferior  lobes  of  the 
cerebellum.      (See  Fig.  15^.) 


■iura   hr^'""' 


S^y^"" 


Fimire  '^9. 


180  ARCHITECTURE    OF    THE    BRAIN 


Figure  30 — Is  a  vertical  section  through  the  middle  lobe 
of  the  cerebellum  showing  the  arbor  vitte.  The  valve  of 
Vieussens  is  seen  to  enter  the  hilus  of  the  middle  lobe  of  the 
cerebellum  and  divide  into  numerous  branches;  these  sub- 
divide into  minute  branchlets  which  are  distibuted  to  the 
leaflets  that  line  the  sides  of  the  fissures  of  the  vermiform 
processes.  The  convolutions  of  the  lateral  lobes  of  the  cere- 
bellum radiate  from  the  central  lobe  and  are  continuous  with 
its  convolutions  and  commissures. 

Figure  31 — Is  a  vertical  section  of  the  lateral  lobe  of  the 
cerebellum,  showing  the  convolutions  and  fissures  of  the  hem- 
ispherical ganglion,  the  corona  radiata,  and  dentate  body. 
The  processus  enters  the  hilus  of  the  cerebellum  and  termi- 
nates posteriously  within  the  corpus  dentatum. 


^^h 


w. 


4 


Figure  30. 


G   '>  f^    'Z   '    f  o  n " 


,  DC  nt^ 


^'^c/.-^^'-       r 


Figure  31. 


182  ARCHITECTUKE    OP    THK    BKAIN. 


Figure  32 — Is  a  transverse  section  of  the  crura  cerebri 
midway  between  the  upper  border  of  the  pons  Varolii  and 
the  optic  tract,  and  illustrates  the  crustse  and  the  parts  which 
form  the  tegmentum. 

Figure  33 — Is  a  section  of  the  crura  cerebri,  immediately- 
above  the  pons  Varolii,  and  shows  the  same  parts  that  are 
seen  in  figure  32. 

Figure  34 — Is  a  section  of  the  pons  Varolii  midway  be- 
tween its  upper  border  and  the  emergence  of  the  fifth  nerves. 
It  shows  the  fourth  ventricle,  fasciculi  teretes,  median  fissure, 
processus,  fillet,  and  the  deep  and  superficial  layers  of  the 
pons. 

Figure  35 — Is  a  transverse  section  of  the  pons  Varolii  on 
a  level  with  the  fifth  nerves,  the  roots  of  which  are  seen  on 
either  side. 

Figure  36 — Is  a  section  of  the  medulla  oblongata  through 
the  olivary  bodies  and  the  restiform  nuclei. 

Figure  37 — Is  a  section  through  the  medulla  oblongata  at 
the  decussation  of  its  crossed  pyramidal  tracts.  The  anterior 
cornua  of  grey  matter  are  interrupted,  and  the  posterior  cornua 
assume  a  rounded  form. 

Figure  38 — Is  a  section  of  the  spinal  cord  showing  the 
arrangement  of  its  grey  and  white  colums,  its  commissure  and 
central  canal. 


let    (X 


Figure  3'i. 


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Fia,iiie  35. 


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DecussaTnPy^'. 


Figure  37. 


itrr^^  Fund.RKZ 


Ficuro  34. 


Pos-t.MlcJ   Fss  /  'tolumr    o;  Ga.ll 

Figure  38. 


NDEX  OF  CONTENTS. 


PAGE 

Membranes  of  the  brain 5 

The  cerebro  spinal  axis 8 

The  cerebrum 12 

Dissection   18 

Cerebellum 36 

The  pons  Varolii 40 

The  medulla  oblongata  and  spinal  cord 51 

Recapitulation  of  the  tracts  of  the  cerebro  spinal  axis 63 

Central  origin  and  relation  to  the  cranial  nerves   70 

The  cerebral  hemisphere 106 

Cerebral  localization 128 


NDEX  OF  ILLUSTRATIONS. 


FIGURES 

Surface  of  the  cerebrum 1  and  2 

Corpus  callosum  and  superior  longitudinal   commissure 3 

Fornix  and  lateral  ventricles 4 

Velum  interpositum  and  choroid  ple.xus 5 

Basal  ganglia  and  superior  surface  of  cerebellum 6 

Base  of  the  brain  and  lateral  veiw  of  internal  capsule 7 

Posterior  view  of  the  intermedia    8 

Lateral  view  of  the  intermedia 9 

Posterior  dissection  of  the  intermedia 10 

Dissections  of  crus  cerebri,  pons  and  medulla  ....  .11,   12,  13,  14 

Fourth  ventricle,  processes  and  red  nuclei 15 

Relations  of  cerebellar  peduncles   and  corpus  dentatum 15| 

External  surface  of  the  hemispherical  ganglion 16 

Internal  surface  of  the  hemispherical  ganglion 17 

Insula IS 

External  capsule  and  external  longitudinal  commissure    19 

Lenticular  nucleus  and  external  longitudinal  commissure  and 

external  capsule 20 

Relations  of  crusta,  fillet,  thalamus  and  external  longitudinal 

commissure     21 

Relations  of  anterior  commissure,  crusta,  fillet,  thalamus   ...  22 

Intrahemispherical  view  of  the  internal  surface  of  hemisphere  23 

Relation  of  the  convolutions  and  fissures  to  the  skull 23^ 

Cerebral  localization,  after  Horsley 24 

Cerebral  localization,  after  Ferrier 25 

Median  section  of  the  brain 26 

Upper  surface  of  the  cerebellum .      27 

Anterior  view  and  hilus  of  cerebellum 28 

Inferior  surface  of  cerebellum 29 

Arbor  vita; 30 

Section  of  lateral  lobe,  cerebellum 31 

Section  of  crus  cerebri,  tegmentum  and  crusta 32 

Section  of  crus  cerebri  above  the  pons  Varolii 33 

Sections  of  pons  Varolii 34  and  35 

Section  of  medulla  oblongata 36 

Section  of  decussation  of  anterior  pyramid 37 

Section  of  spinal  cord 38 

Shirty-six  topographical  sections  of  the  brain  .  .  .  .pages  137  to  173 


INDEX. 


Anterior  commissure  of  third  ventricle, 

p.  20;  Figs,  6-13-14;  Sec.  14-15. 
Anterior  median  fissure,  p.  9;  Figs.  7-9. 
Anterior  peduncles  of  corpus  callosum, 

p.  21;  Figs.  7-26, 
Anterior  pyramids  of  medulla  oblonga- 
ta, pp.  57-59;  Figs.  9-11. 
Anterior  root  zone  of  spinal  cord,   pp. 

47-57;  Figs.  7-10  to  13. 
Aperculum,  p.  111. 
Acquaduct    of    Sylvius,    or   iter,   p.  27; 

Figs.  26-27-32-33. 
Arachnoid  membrane,  pp.  5-7. 
Arbor  vits,  p.  37;  Figs.  26-30, 
Arciform  fibres  of  medulla,  p.  60;   Figs. 

7-9. 
Basal  ganglia,   pp.  17-29;    Figs.  6  to  10; 

Sec   10  to  18. 
Basilar  groove,  p.  9;  Figs.  9-27. 
Bichat,  fissure  of,  pp.  10-13. 
Brachia,  p.  28,  Figs.  6-8-9-13-14. 
Burdach's  column,  p.  56. 
Calamus  scriptorius,  p.  48;  Figs.  8-10. 
Caudate  nucleus,  pp.  30-17-23;  Figs.  4- 

6-7;   Sec.  11, 
Central    canal    of    spinal   cord,    p.    10; 

Figs   8-10. 
Central  origin  of  cranial  nerves,  p.  70. 
Cerebrum,  pp.  8-12. 
Cerebrum,    superior   surface   of,    p.    12. 

Figs.  1-24-26 
Cerebrum,    inferior   surface   of,    p.    12; 

Figs.  2-7. 
Cerebrum,  structure  of,  p.  14. 
Cerebral  hemisphere,  p.  106;     Figs.  16- 

17. 
Cerebral  localization,  p.  128;  Figs.  23;^- 

24-25. 
Cerebellum,   pp.  8-36;     Figs.  6-7-27  to 

31. 
Cerebro-spinal  axis,  p.  8. 
Choroid  plexus,  pp.  24-23-7;  Figs.  4-5. 
Choroid  plexus  of  third  ventricle,  p.  25. 
Note.— Sec.  signifies  Topographical  Sectio 


Claustrum,  pp.  17-34;  Sec.  10  to  18. 

Clavate  nuclei,  p.  48;  Figs.  8-10. 

Commissure  of  gyrus  fornicatus,  p.  Ill; 
Fig.  3-23. 

Comparison  of  cerebrum  and  cerebel- 
lum, p.  38. 

Connection  of  superior  and  inferior  pe- 
duncles of  the  cerebellum  with  the 
corpus  dentatum,  p.  38. 

Convolutions  of  hemispherical  ganglion, 
p.  111. 

Cordon,  pp    111-107;   Fig.  17. 

Cornua  of  lateral  ventricles,  p.  22;  Fig. 
5 

Corona  radiata  cerebrum,  pp.  16-18; 
Figs.  3  to  6, 

Corona  radiata,  cerebellum,  p.  25. 

Corpora  albicantia,  p.  15;   Figs.  7-9. 

Corpora  geniculata,  pp  28-29;  Figs.  7- 
8-9 

Corpora  quadrigemina,  p.  27;  Figs  6- 
8-9. 

Corpus  callosum,  p.  18  13-16;  Figs.  3- 
8-23-26 

Corpus  fimbriatum,  pp  23-24;   Figs,  4-5. 

Corpus  dentatum,  p,  37;   Figs.  8  to  15}^. 

Crests  of  corpus  callosum,  pp.  18-23; 
Figs.  3-8. 

Crossed  pyramidal  tracts,  pp.  56. 

Crusfa,  pp.  15-34;  Figs.  2-7  to  12. 

Decussation  anterior  pyramids  of  me- 
dulla. Figs.  7-11  to  14. 

Decussation  corpus  callosum  and  inter- 
nal capsule,  p.  16;  Figs.  3-8;  Sec. 
18-19. 

Direct  cerebellar  tract,  p.  56. 

Direct  pyramidal  tract  column  of  Turck, 
p.  55. 

Dissection,  p.  18. 

Dura  mater,  p.  5. 

Eminentia  collateralis,  p.  22;   Fig.  5. 

External  basal  ganglion  cerebrum,  p.  33; 
Figs.  9-12-20. 


INDEX — Continued. 


External  basal  ganglion  cerebellum,  p. 

39. 
External  capsule,  pp.   17-33;  Figs.   7-9- 

19;  Sec.  10  to  18. 
External    longitudinal    commissure,  pp. 

19-20. 
Falx  cerebri,  p.  5. 
Fascia  dentata,  p.  111. 
Fasciculi  teretes,  pp.  44-47;  Figs.  10-15- 

25. 
Fifth  ventricle,  p.  24;  Figs.  4  to  8. 
Fillet  or  lemniscus,  p.  43;  Figs.  10  to  14, 

26. 
Fillet  fibres  from  fourth  ventricle,  p.  47; 

Figs.  11-12-13. 
Fissures,  anterior  median,  p.  9. 
Fissures,  longitudinal,  p.  10. 
Fissures,   Bichat   or  transverse,   pp.  10- 

13-23;  Figs.  4-5. 
Fissures,  posterior  median,  p.  10. 
Fissures,  olfactory,  p.  15. 
Fissures,  Sylvius,  pp.  13-108;   Figs  2-7- 

16-24. 
Fissures,  Rolando,   p.  108;    Figs.   24-25- 

231^. 
Fissures,  calloso-marginal,   p.  110;    Fig. 

17. 
Fissures,  parieto-occipital,   p.  110;   Fig. 

17. 
Fissures,  calcarine,  p.  110;   Fig.  17. 
Flocculi,  p.  36;  Figs.  7-28, 
Foramen  of  Monro,  p.  23;  Figs.  4-5. 
Foramen  of  Majendie,  p.  64. 
Formatio  reticularis,  p.  20. 
Fornix,  p.  23;  Fig.  4. 
Fourth  ventricle,  pp.  48-11;   Figs.  8-10- 

13-15-26. 
Frontal  lobes,  p.  12;  Fig.  2. 
Fundamental  root  zone,  pp.  15-28-46-47- 

55;  Figs.  8-9-11-12-13. 
Fusiformis    lobe    of    thalamus,    p.    32; 

Fig.  6. 
Ganglion  of   pons   Varolii,  p.  45;    Figs. 

34-35. 
Geniculate  bodies,  p.  14;  Figs.  8-9-11-12. 
Genu  of    corpus  callosum,  p.  21;    Figs. 

4-5-6-26. 
Genu    of    internal    capsule,    pp.    24-30; 

Figs   4-7-8. 
Globus  pallidus,  p.  33. 
Cowers'  sensory  tract,  p.  57. 


Great  longitudinal  fissure,   p.  10;    Figs. 

1-2-17-24-26. 
Groove    separating    corpura    quadrige- 

mina,  p.  10;  Fig.  8. 
Gyrus  fornicatus,  p.  18;   Figs.  17-26. 

Hemispherical    ganglion    cerebrum,  pp. 

17-106;  Figs.  16  to  23. 
Hemispherical   ganglion   cerebellum,  p. 

38;  Fig.  151^. 
Hilus  of  cerebrum,  p.  18;  Figs.  2-17. 
Hippocampus  major,  minor,  p. 22;  Fig. 5. 
Incisura  cerebelli,  p.  10;  Figs.  27-29. 
Infundibulum,  p.  26;  Figs,  7-9. 
Insula,  p.  17;  Fig.  18. 
Internal  capsule,  pp.  16-29;  Figs.   4  to 

14,  18  to  22;  Sec.  10  to  19. 
Internal  layer  corona  radiata,  p.  20. 
Internal  basal  ganglia,   p.   30;    Fig.   6; 

Sec.  9  to  17. 
Internuncial  fibres,  p.  19;   Figs.  3,  18  to 

22. 
Interpeduncular  space,   pp.   9-26;    Figs 

2-7-9, 
Iter,  p.  11;   Figs.  10-15-26-27. 
Lamina    cinerea,    pp.    21,   26;    Figs.    9- 

11-12. 
Lateral  ventricle,  pp,  22-11;   Fig.  4. 
Layers  of  corona  radiata,   p.   20;    Figs. 

20-21;  Sec.  25. 
Layers  of  pons  Varolii,  p   45;    Figs    9- 

11-12. 
Lemniscus,  see  fillet,  p.  43;   Figs.  10  to 

14,  26. 
Lenticular  nucleus,  pp.  33-17;    Figs.  7- 

9-12-20;  Sec.  17. 
Ligamentum  dentatum,  p.  6. 
Lobes  of  cerebellum,  p.  36. 
Loci  cserulii,  p.  49. 
Locus  niger,  p.  45;  Figs.  10-11-12  32-33; 

Sec.  20-21. 
Longitudinal  commissures,  p.  20;   Figs. 

3-4-9-18  to  21. 
Lyra,  p.  24;   Figs.  5-6. 
Median  fissure,  p,  9, 
Medulla  oblongata  and  spinal  cord;  pp, 

57-51;  Figs   2  to  15. 
Middle  commissure   third   ventricle,   p. 

26;  Figs.  6-26. 
Membranes  of  the  brain,  p.  5. 
Mixed  lateral  tract  of  spinal  cord,  p.  57. 


INDEX— Continued. 


Nates  (see  corpora  quad,  page  27.) 
Nerves  of  Lancisi,  p.  21;  Fig.  3. 
Nucleus  of    pons  Varolii,    p.   45;    Figs. 

34-35. 
Occipital  lobes,  p.  13. 
Olfactory  nerve  bulb  and  fissure,  p.  12; 

Figs,  2-7. 
Olivary  bodies,  p.  60;  Figs.  9  to  14. 
Olivary  fasciculus,  pp.  47-60;  Fig.  12. 
Optic  commissure,  p.  26;  Figs.  2-7. 
Peduncles  of  cerebrum,  p.  14;   Figs.  2- 

7-8-9-10-26-27. 
Pes    hippocampi,     accessorius,     p.     22; 

Fig.  5. 
Pia  mater,  p.  6. 

Pillars  of  pineal  body,  p.  27;   Figs.  6-8. 
Pineal  gland,  p.  27;   Figs.  6-8. 
Pison,  p.  31;  Fig.  6. 
Pituitary  body,  p.  26. 
Pons   Varolii,    p     40;    Figs,  7-9   to    14. 

Structure  of,  p.  42.     Dissection  of,  p 

44;  Figs.  11  to  14. 
Posterior  median  column.  Gall's,  p.  55; 

Figs.  8-10, 
Posterior  median   fissure,    p.    10;    Figs, 

8-10, 
Posterior  pillars  of  fornix,  p.  24;   Figs, 

4-5, 
Posterior  pyramids   of    medulla,   p,  57; 

Figs,  8-10-15, 
Posterior  root  zone,  Burdach's  column, 

p,  56, 
Processus,  pp,  15-28;  Figs.  8  to  15-27-28, 
Pulvinar,  p,  32;   Fig,  0, 
Puncta  vasculosa,  p,  19;  Fig,  8, 
Putamen,  p.  33. 
Raphe   of    cerebral    peduncles,    p.    14; 

Figs.   26-27  33.     Oval   opening  in,  p. 

43;  Fig.  26. 
Raphe  of  corpus  callosura,  p.  21;  Fig.  3. 
Recapitulation  of    tracts  cerebro-spinal 

axis,   p.  63. 
Red  nucleus,  p.  32;   Figs.  10-13-15;  Sec. 

19-20. 
Restiform  body,  p.  61;   Figs.  8  to  15. 
Restiform  nucleus,  p.  49;  Figs.  8-10-36. 
Restiform  system,  p.  62. 
Restiform    triangle,   pp.   47-61;    Figs.   9 

to  13. 
Section  of  corpus  callosum,  p.  21;   Fig. 

26. 


Septum  lucidum,  pp.  22-23-24;   Figs.  4 

to  10-26. 
Spinal  cord,  pp.  8-51. 
Splenium,  p.  21;  Figs.  4-5-26. 
Striae,  longitudinales,  p.  21;  Fig.  3. 
Strife,  transversEE,  p.  49;  Figs.  8-10. 
Structure  of  cerebrum,  p.  14. 
Subarachnoid  spaces,  p.  6. 
Subthalmic    ganglion   (red   nucleus),    p. 

32;  Figs.  10-13-15. 
Superior  longitudinal  commissure,  p.  21; 

Figs.  3-23. 
System,  cerebello  spinal,  p.  68. 
System,  fillet,  p.  67. 
System,  ganglionic,  p.  64. 
System,  motor,  p.  66. 
System,  organic  and  sensory,  p.  68. 
System,  respiratory  reflex,  p.  68. 
System,  ventricular,  p.  63. 
System,  visual  reflex,  p.  66. 

Taenia  semi  circularis,   pp.  30-23:    Figs. 

6-7-8. 
Tegmentum,  pp.  15-16-34;  Fig.  32. 
Temporal  lobes,  p.  12. 
Tentorium  cerebelli,  p.  5. 
Testes  (see  corpora  quad.)  p.  27. 
Thalamus  opticus,    pp.    17-23-31;    Figs. 

6-8-10. 
Third  ventricle,  pp.  26-11;   Figs.  6-8-10- 

1.V26. 
Tracts  of  spinal  cord,  p.  55;   Figs   7  to 

15-38. 
Transverse    fissure   of    Bichat;    p.    10; 

Fig.  26. 
Triangle  to  illustrate  aphasia,  p.  19, 
Tnber  cinereum,  p,  26;   Figs,  7-9. 
Tubereulum  Thalami,  p.  32;  Fig.  6. 

Valve  of  Vieussens,   pp.  10-28;  Figs.  8- 

10-26. 
Vena  Galeni,  p.  25;   Fig.  5. 
Velum  interpositum,   pp.  10-25;   Fig.  5. 
Ventricle  of  corpus  callosum,  p.  18. 
Ventricular  system,  pp.  10-63. 
Vermiform  processes  of  cerebellum,  p. 

36;  Figs.  26-27-31. 
Vertical  depression  of  crus  cerebri,  pp. 

14-15;  Figs.  8-9. 
Vesicular    columns    of    Clarke,    p.    52; 

Fig.  38. 
Vesicular  columns  of  spinal  cord.  p.  52. 


FULLER  ANATOMICAL  CO., 


MANUFACTURERS   OF 


ANATOMICAL   AND    PATHOLOGICAL   MODELS, 
GRAND  RAPIDS,  MICH. 


Casts  nqade  of  soft  tissues,  ttinqors,  etc.,  of  natural  size  aqd 

sl^ape  arid  representing  niiriute  details. 
Tl^e  specirnens  returned  ■wit]:]out  injury. 
Plates   taKen   direct  frorn  tl^e  object  for  tl^e   illustration   of 

booKs  and  papers  a  specialty 


PRICES  OF  MODELS  OF  THE  BRAIN. 

Student's  set,  of  six  pieces  in  a  box,  represented  b}'  figures   1 

to  7  and  16  and  17 $15.00 

Six  lateral  dissections  of  hemispliere  on  a  placque 15.00 

Dissections  of  the  intermedia,  six  pieces.  Figs.  8  to  14- 25.00 

Topographical  sections  natural  shape  of  brain,  in  a  box -25.00 


i&° Dr.  Fuller's  models  of  the  brain  were  awarded  the  medal  and 
diploma  of  the  World's  Columbian  Exposition,  and  were  purchased  bv  the 
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